I've been doing this for awhile but just now wonder about the "teams" I remember reading about. I downloaded the screensaver and am not attached to any team. Is it too late to get attached to a team? How do I do that? Is it better to be attached to a team or do this as an individual?

Thank you to anyone who answers my questions.

Teams are like a social club; you can join one if you wish.
And, like social clubs, they each have their own areas of interest, so you should find out from the descriptions of each, which one you like the most.
UNLIKE social clubs, you can only join one for a given project, but you can join a different one in each project for which you crunch.

The 'fees' for teams, is that they get a "copy" of your credits to add to their team total.

And you didn't actually download a "screensaver", you downloaded a science application, most of which have an associated screensaver.
Which for some projects, such as the climate predication projects, can use up a lot of processor time to create; time better spend running the science app.