As we have seen in the previous section, the client's job is to request things. He requests a website's files or anything served from a server. The connection of a client to a server is shown in the next figure, where the client makes a request through an application:

Note that a client is usually a person, but without doubt, a client can be another server. Client-server communication is a basic idea, where the client requests over HTTP or HTTPS protocol files from a server. If the server does not have those files then, the server itself can request them from another server or respond with Error 404: File not found.