A class browser is like a special kind of toy box where you can see all the toys you have, grouped by what kind they are. It helps you find a toy you want to play with very quickly, because you can see where it is and what it looks like.
In the same way, a class browser helps people who work on computer programs to find pieces of code that they need to work on. Just like toys, computer programs are made up of small parts, called classes, that work together to make the whole program work.
A class browser lets people see all the different classes in a program, and how they relate to each other. It helps them quickly find the class they need to work on, and see what it does and how it works.
It's a very helpful tool for programmers and developers, and it can save them a lot of time and make their work easier.