Are Credits like paper currency, are do we have some sort of futuristic 'credit chip' or something like that?

Edit: Ya'know since I'm asking that I'm also wondering where the hell AcadeMMO is. I gather that it's in America/UK based on the fact that English seems to be required, but is it like, surround by a small town? Or in a massive city? Or in the middle of nowhere? I'm also wondering if students are given free roam outside of the school outside of class hours.