There's a guide bookmarked for you already on your iPhone. Go to Safari, then open the Bookmarks panel. Scroll down to the bottom, you should see "iPhone User Guide"
FaceTime is Apple's attempt at easy video calling. You can FaceTime anybody with an iPhone 4, 4S, iPod touch 4th generation, iPad 2, or Mac (as long as they have FaceTime installed, which if it didn't already come with their computer, is a $0.99 app).
For iPhones, you just need to dial their phone number via FaceTime. For everything else, just an email address. Both of you have to be on wifi, though.
There is a guide to FaceTime under the aforementioned user guide. Go to the Phone section, and there will be a link to the FaceTime guide in the middle of the page.