Q: What's the "Other..." Account? Why am I locked out of my own Mac?

I was using my MacBook Pro and going through finder to delete some old files, and I tired opening a video and it just froze finder, I could still use other applications such as Firefox but finder completely froze so I tried Roy's famous technique of "have you tried turning it off an on again" and when I did Apple yet again prompted me to instal the updates, I rarely install updates since I used to on my iPhone and it always caused problems, in any case I thought that crash might of had something to do with that so I agreed and it installed and turned off, when it restarted the login screen came up with a login called "Other..." I don't know what this is, both my usual logins aren't there & this "Other..." Login is requesting a name and password, I've tried everything but nothing works, why isn't my normal login account there? I've tried command R for recovery but it just makes that sound when a keyboard shortcut isn't available, can anyone help me get back into my account and also disable this "other..." crap. I have a university deadline in two days & all of the work is on this machine, so speed would be much appreciated, thank you