Any communication process needs a sender, who sends the message (may be a request) and a receiver, who receives the message sent to him. This communication process may further progresses when the message sent is a request. Then most of the times, the receiver again responds to the request and sends a message (response) back to the other side.
In a web application, client (generally a browser) plays the role of sender and sends the message (usually request for a page) to the server( web server). Then the server processes the request and replies with a message(requested page). For instance, when type www.suvendugiri.com in the address bar of the browser and press ENTER or click on the GO button, it sends a request to the server where the website is hosted. Here the request is to display the default page of my blog. Now after processing the request , server sends the response. Now the page is rendered to the browser in HTML format. This type of communication is termed as client-server communication.
INFORMOTIONS.COM has a nice idea to describe all this: (check below)
” This client/server interaction is a lot like going to a French restaurant. At the restaurant, you (the user) are presented with a menu of choices by the waiter (the client). After making your selections, the waiter takes note of your choices, translates them into French, and presents them to the French chef (the server) in the kitchen. After the chef prepares your meal, the waiter returns with your diner (the results). Hopefully, the waiter returns with the items you selected, but not always; sometimes things get “lost in the translation.” “