2 users is normal. One is console and has been idle for 15 hours. One is you logged in right now. Just make sure you run a browser other than Safari or at least shut down "automatically open safe files after download." and you shouldn't have to worry about the present malware/trojan that is going around for OS X.
If you run another terminal window, a third copy of you will show up. Nothing to see here. Move along.
If you run another terminal window, a third copy of you will show up. Nothing to see here. Move along.