Although Google Buzz is admittedly inspired from the Google Wave project, it is a social networking tool (kind of advanced Twitter), while Google Wave is a complete online collaboration tool that would be more suitable for working on a group project for instance (but not only).
There are already concerns about Google Buzz making you more social than you'd want so you should ensure that you control who your followers are, who you're following yourself, the privacy level of your buzz, and if you want your profile public or not.
Google Buzz is really a social networking thing, so the non-Facebook/mySpace people should ultimately consider scrolling to the very bottom of the Gmail page to turn Buzz off.
Introduction to Google Buzz:
Introduction to Google Wave
The short version:
The long version:
I want Google Wave!