What is a Server?

Simply put, a server is a computer that provides some kind of content, data, or information.

The image of a server is a machine shaped like a vending machine. It is a hardware consisting of components such as a CPU that calculates instructions, memory that temporarily stores data, and storage that holds data for the long term. (The personal computer we use can also be used as a server since it contains the same components as a server.)

In a simple example, if we write source code in some programming language and run it on a server, it becomes an application server, and if we install middleware such as MySQL on the server, it becomes a database server.

The most important thing to note here is that "˜servers' taken from the physical aspect are all the same vending machine-like machine, and the hardware itself is almost the same for all of them. If you are running an application, it is an application server, if you are installing middleware for DB, it is a database server, and if you are running scripts for batch processing, it is just called a batch server.

So, in this article, I will give a brief overview of the various servers.

First, before we do that, please understand that "˜server' can be viewed in the following four ways.

• Server function/role type
• Server delivery system type
• Server delivery technology type
• Server physical type

It is important to understand this point because if you are mixed up here, you will not know which concept of server you are describing.

Perhaps those who do not grasp the concept of servers well have the four categories of servers mixed up, so they think of servers as something fluffy.

Let's take a look at each of these servers in detail.

By server function/role

First, let's examine server types from the perspective of their functions and roles - what specific services they provide within a system.

Web Server

The essential web server for applications. This server receives user requests, passes them to the backend for processing, then receives the processed results from application servers and returns them to users.

Think of it as the "front desk" between users and applications. Servers with middleware like Apache or Nginx installed are typically called web servers.

Application Server

The application server runs applications built with languages like Ruby, Python, or Java. It parses request data from web servers, performs database operations (storing/retrieving data), and returns processed data to web servers.

Database Server

A database server runs middleware like MySQL or PostgreSQL for strict data management. It efficiently stores and retrieves data based on SQL queries from application servers.

Mail Server

Mail servers typically consist of three components:

1. SMTP server (sending)
2. POP3 server (receiving)
3. DNS server (explained later)

Basic email flow:

1. User A → SMTP server
2. SMTP queries DNS for recipient's POP3 server IP
3. SMTP → POP3 server
4. User B retrieves from POP3 server
   (Simplified - actual process is more complex)

File Server

As the name suggests, a file server manages and shares files across multiple computers. Modern equivalents include NAS (Network Attached Storage). Services like Google Drive are essentially file servers.

FTP Server

An FTP (File Transfer Protocol) server handles file transfers. For example, when publishing a blog:

• Blog resources live on a blog server
• FTP clients (like FileZilla) send files to the server
• The receiving blog server acts as the FTP server during transfer

Directory Server

Provides directory services (not to be confused with file directories). Uses LDAP protocol to centrally manage network computer information (e.g., IP addresses). Microsoft's Active Directory is a well-known example.

DNS Server

Performs name resolution, mapping domain names to IP addresses. Imagine it maintaining a lookup table connecting blog.example.com to its server's IP address.

Cache Server

Stores temporary copies of data to improve speed and reduce load. Often used with CDN (Content Delivery Network) technology. For example, during a TV shopping rush, cache servers handle traffic spikes by serving cached content instead of overloading the origin server.

Batch Server

Dedicated to batch processing - executing scheduled, resource-intensive tasks (daily data processing, etc.). Separated from main servers to prevent performance interference.

DHCP Server

Uses DHCP protocol to automatically configure network settings for devices joining a network - like a helpful admin assigning IP addresses to new computers.

Authentication Server

Specializes in verifying user credentials. Large systems often use dedicated authentication servers for centralized, secure credential management in protected network zones.

SSH Server

The receiving end of SSH (Secure Shell) connections. When you SSH into an AWS EC2 instance, that EC2 is the SSH server. SSH replaced the insecure Telnet protocol with encrypted communications.

Proxy Server

Acts as a gateway between networks. Benefits include:

• Filtering external connections
• Hiding internal IP addresses
• Caching content
• Load balancing

"Proxy" means "intermediary" - these servers process requests on behalf of others.

This classification covers major server types based on their primary functions in systems and networks. Each plays a distinct role in modern computing infrastructure.

Server Provisioning Structure

Now, let’s discuss how servers are provided. As we’ve seen, servers can run various middleware and applications to deliver different services. But how do you actually obtain a server when you need one?

Generally, there are two main approaches:

1. Renting a server
2. Buying a server

First, let’s look at rental servers.

Rental Servers

As the name suggests, rental servers are leased from providers—similar to renting a DVD or other service. Pricing typically depends on the server’s specs (CPU, memory, etc.), with most providers offering monthly subscription plans.

Rental servers can be further categorized into different types:

1. Dedicated Server

A dedicated server is an entire physical machine (like a vending machine) leased exclusively to you.

Pros:

• Full customization freedom
• Access to 100% of the server’s resources
• Stable performance, even under heavy traffic

Cons:

• More expensive than shared servers

2. Shared Server

A shared server is used by multiple customers simultaneously.

Pros:

• Cost-effective for personal blogs or small apps

Cons:

• Performance may be affected by other users
• Less secure for sensitive data due to shared resources

3. Cloud Server

Cloud servers (e.g., AWS, GCP, Azure) are essentially a modern form of rental servers. They allow flexible scaling and often let you choose between dedicated or shared setups via a console or API.

Owned Servers

The term “owned server” isn’t commonly used, but for clarity, it refers to physically owning the hardware—unlike renting.

1. On-Premises (Corporate) Server

Before cloud computing, most companies ran their own on-premises servers in private data centers. While some enterprises still use this model, many SMBs and web-based businesses have migrated to the cloud.

2. Home Server

A home server is privately owned by individuals. While a regular PC can function as a server, it’s not ideal for performance or reliability. Common home server setups include:

• Workstations (high-performance PCs)
• Raspberry Pi (low-cost mini-computers)

Server Provisioning Technology Type

Next, let's examine the two main server provisioning technologies:

1. Bare Metal Servers

A bare metal server is a physical server with no pre-installed software—just raw hardware. While definitions may vary slightly between vendors, this is the core concept.

• The term "bare metal" comes from "exposed metal" (referring to direct hardware access).
• Now available through some cloud providers (though not all offer it).
• Uses high-performance computing resources, making it ideal for:
  • Mission-critical applications
  • Low-latency workloads
  • Specialized hardware needs (e.g., GPU clusters)

2. Virtual Servers

Virtual servers are the modern standard for efficient resource usage. This technology allows:

• Consolidation: Multiple virtual servers to run on one physical machine (via a hypervisor).
• Isolation: A single physical server to be partitioned into multiple independent virtual servers.

Current Trends:

• Often paired with containerization (Docker, Kubernetes) for even lighter virtualization.
• The opposite of bare metal—fully software-defined environments.

Physical type of server

Finally, let's examine the three main types of physical server hardware configurations:

1. Tower Servers

• The most basic business-grade servers
• Slightly larger than desktop PCs (can sit on/under a desk)
• Commonly used by SMBs with 1-2 units for office workloads
• Pros: Space-efficient, easy to deploy
• Cons: Not scalable for large deployments

Think of them as "grown-up desktop computers" for office use.

2. Rack Servers

• Designed for data center use (mounted in server racks)
• Resemble "vending machine" modules
• Allow consolidation of:
  • Servers
  • Network switches
  • Storage arrays
• Pros:
  • High density (saves space)
  • Centralized management
  • Better cooling efficiency

The standard choice for professional IT infrastructure.

3. Blade Servers

• Ultra-compact "blade" modules stacked in enclosures
• Each blade is an independent server (CPU/memory/storage)
• Key advantages:
  • Hot-swappable (replace failed units without downtime)
  • Simplified cabling (shared power/networking backplane)
  • Energy-efficient cooling
• Ideal for:
  • High-density computing
  • Modular scalability

Like "server LEGO blocks" – compact and modular.

summary

In this article, I have tried to paint an overview of the server from various angles. I have only given a rough description, so if you have extra time, you will feel even more comfortable if you do more in-depth research on the above words!

I am sure there are more "˜servers' than I have described here. I am sure there are more "˜servers' than I have described here, but I think it is important to determine which tier of servers you are talking about in that case as well.