Hello and welcome. I have a Trek hybrid and love it. It is a good "starter" bike; maybe you will want to upgrade, maybe not.

I got good advice from this forum on looking at used bikes (if you are new to cycling you should ask someone with more experience, or maybe a bike shop, to check used bikes you look at):

http://forums.teamestrogen.com/showthread.php?t=41950

And here's an illustration showing bicycle parts:

http://www.jimlangley.net/wrench/bicycleparts.html

Once you get your bike, find out of any groups near you have "beginner" rides. Classes in bike repair are a good way to get to know your bike, meet people who ride, and gain confidence about minor repairs.

Hope you find a good bike, and continue to ask questions here. I've gotten great advice and guidance from this very knowledgeable group.