Synthetic Class in Java

Question

What is a synthetic class in Java? Why should it be used? How can I use it?

Answer 1

Well I found the answer to the first question on google:

A class may be marked as synthetic if it is generated by the compiler, that is, it does not appear in the source code.

This is just a basic definition but I found it in a forum thread and there was no explanation. Still looking for a better one...