From Fedora Project Wiki
How To File a New Bug
Introduction
This document will a newbie to file a bug (in other words, newbies will be able to report bugs). This document is made in keeping the Redhat bugzilla , but this can help to file bug report to any other bugzilla instance.
What is a Bug ?
In simple words, a bug is a problem or error in any software. If the software is not working in the way it is supposed to work, then we say the software is having a bug. If the developers (the people who write these software) come to know about any new bug, they try to solve it to make the software better.
So, if you are facing a bug then you should report it to upstream developers. Bugzilla is a software what we use for this purpose.