The Hypertext Transfer Protocol (HTTP) is the modern Internet's courier. It is responsible for the delivery of vast amounts and different types of data online such as web pages, images, video, audio and more.

HTTP is based on a client-server architecture. A client is anyone who requests a resource from a web server.

An example is you (the client) watching a cat video (the resource) on YouTube (the server).
Copy

The communication between the client and the server is actuated by the so-called transactions. Each transaction consists of a request, sent by the client to the server, and a response, sent back by the server to the client. Generally, a request describes what action the client wants the server to perform and the response contains information about the outcome of the action.

The client could request a specific web page from the web server, or they could try to upload a file to it. The server would then respond with information about whether or not the action was successful and any accompanying data.
Copy

Requests and responses are collectively known as **messages**.
Copy