Car died... and now it won't start... help!!!

is there any chance of it being the alternator? because when trying to crank it today... it sounded like normal when i tried 2 crank it... it just wouldn't start up... today... i was gonna show someone what it would do... and it would turn over... but with a harsh sound to it... sounded very weird... maybe it had just enuff to keep it going the other day... and not enuff 2 even turn over good now? then again i have no idea about this mechanical stuff... i'm a car audio and soccer guy lol