Client -

A client typically refers to a device or software program that connects to a web server to access web-based resources or services. These clients are typically web browsers, such as Google Chrome and other which are used to display and access web pages and other content.

Server -

A server is a device or software program that provides resources or services to clients over the internet or a private network. In the context of web development, clients are typically web browsers or mobile apps that connect to the server to access web-based resources or services.

Ok! It looks very technical, right? let me explain to you simply, for example, if you are going to a shop for buying cake now for buying the product you will communicate with the shopkeeper to buy the product. Now, you the person asking for the product acting as the client and the shopkeeper you asked the product for is the server here. So, this is how a client and server communicate.