If you don't already know, 'Beta 2' means that the program should only be installed by people who are prepared to risk potential computer problems. Before it is released to everyone, it will go through the 'release candidate' stage, and then released for everyone.
Features that IE7 include are:
- Tabbed browsing
- Phishing filter (tells you if you visit a fraudulent website)
- Improved rendering engine
- Lots of other stuff as well.