It is easy to explain what part of a client/server relationship you would like to handle by analyzing the frontend (client side) and the backend (server side) of a website.
The client side means that your focus is on the front end, which is the part of the website you can view in the browser. You can think of a frontend as everything a user can see and experience when they refer to the site.
The server side,"back end" is a part of the site that is not easily visible, but it is responsible for handling a lot of the logic and functionality that makes the site work. The "back end" is simply the place where information is stored, sent, and received behind the scenes.
Web developers can be classified into three separate groups: frontend, backend, and full stack.
In web development, Full Stack Web Developers take care of both sides.
Even if you don't know which of these is better fit for you yet, keep practicing and exploring! The more you do, the more obvious it will be.