Really the main thing you should know is that sex in a porn video and sex between two people who love each other is completely different. There are a lot of things in videos that are fairly unrealistic.
I don't want to go into detail with a 10 yr old but trust me. I don't believe people should watch much sex tapes till they've had some actual sex in real life so they know reality from fantasy.
Some of your questions could be answered at this website.
http://www.teenwire.com/ It's run by Planned Parenthood so it's responsible and accurate info and you won't see any porn.