---
myst:
  html_meta:
    description: "Understand web server options for Ubuntu Server, including Apache, Nginx, and other {term}`HTTP` server technologies."
---

(about-web-servers)=
# About web servers

The primary function of a **web server** is to store, process and deliver **web pages** to clients. The clients communicate with the server by sending {term}`HTTP` requests.

Clients, mostly via **web browsers**, request specific resources and the server responds with the content of that resource (or an error message). The response is usually a web page in the form of {term}`HTML` documents -- which may include images, style sheets, scripts, and text.

## URLs

Users enter a Uniform Resource Locator (URL) to point to a web server by means of its {term}`Fully Qualified Domain Name (FQDN) <FQDN>` and a path to the required resource. For example, to view the home page of the [Ubuntu Web site](https://ubuntu.com/) a user will enter only the FQDN:

```text
www.ubuntu.com
```

To view the [community](https://ubuntu.com/community) sub-page, a user will enter the FQDN followed by a path:

```text
www.ubuntu.com/community
```

## Transfer protocols

The most common protocol used to transfer web pages is the Hyper Text Transfer Protocol ({term}`HTTP`). Protocols such as Hyper Text Transfer Protocol over Secure Sockets Layer ({term}`HTTPS`), and File Transfer Protocol (FTP), a protocol for uploading and downloading files, are also supported.

### HTTP status codes

When accessing a web server, every {term}`HTTP` request received is responded to with content and a HTTP status code. {term}`HTTP` status codes are three-digit codes, which are grouped into five different classes. The class of a status code can be quickly identified by its first digit:

* **1xx** :  *Informational* - Request received, continuing process
* **2xx** :  *Success* - The action was successfully received, understood, and accepted
* **3xx** :  *Redirection* - Further action must be taken in order to complete the request
* **4xx** :  *Client Error* - The request contains bad syntax or cannot be fulfilled
* **5xx** :  *Server Error* - The server failed to fulfill an apparently valid request

For more information about status codes, [check the RFC 2616](https://www.w3.org/Protocols/rfc2616/rfc2616-sec6.html#sec6.1.1).

## Implementation

Web servers are heavily used in the deployment of websites, and there are two different implementations:

* **Static web server**: The content of the server's response will be the hosted files "as-is".
* **Dynamic web server**:  Consists of a web server plus additional software (usually an *application server* and a *database*).

  For example, to produce the web pages you see in your web browser, the application server might fill an {term}`HTML` template with contents from a database. We can therefore say that the content of the server's response is generated dynamically.