I've never used the browser part of Winamp myself. I always close it after installation, and have never opened it back up.
What does it do, and what's bad about it? lol
Basically it's a way for advertisers to annoy you with ads, or to get more info on artists and music. I also closed it when I installed Winamp and it's never been opened since. It's a pain in the a$$ on dialup.