Introduction

The World Wide Web (WWW) (or just the web) is a big store of all sorts of documents (XML, JSON, HTML, MP3, JPG, etc.) accessible through Uniform Resource Locators (URLs). A document in the context of the web is often called a resource. Some resources do not change. They are stored somewhere, and with every request, the same resource will be returned. Such resources are called static. Other resources are dynamic, which means they will be generated on demand.

Communication on the web happens through protocols. In the context of retrieving documents, you use Hypertext Transfer Protocol (HTTP). Hypertext is a special text that holds a link to a resource on the web. Clicking on it opens the resource it points to. HTTP is based on a client-server architecture. In simple terms, a client sends requests, and the server responds. An example of this in practice is the communication between a browser (client) and a website (hosted on a server). Usually, a single server serves many...