iOS Xcode project git repo backup?

I just started using git with my Xcode project. I've got as far as changing a file and committing it. I have a couple of questions though.

1) what else do I need to know about Xcode implementation? I've never used source control before. I keep seeing discussion of a .gitignore file. Is that something I need to set up? I'm more or less using it as protection from breaking my projects when adding new features.

2) I tend to switch between 2 computers. Where is the local git repository stored? Can I just continue to copy my project folder over to my other computer?

Thanks guys!