I need to know about computers?

Hey I'm 13 so this might need to be dumbed down a little, but I'm a PC gamer and currently have the HP ENVY Phoenix 810-460 (heres a link http://store.hp.com/...ame=specs) and the monitor is here http://store.hp.com/...eats-audio. This was my first major gaming PC. (I had a laptop before but it was horrible) I will probably just keep updating it as time goes on, but I basically just need to know about the parts of a computer. What I don't understand is what makes one motherboard better than another, how the same amount of gigabytes/terrabytes on one harddrive might be worse or better than the same amount on a different type, basically I don't understand what a video card is, et cetera. Can someone basically just give me a somewhat dumbed down lesson of what everything does and does not do?

P.S. On it I play all games from Call of duty to Garry's Mod to minecraft to some retro.

Suggestion, look into A+ certification guides. Will give you most of the answers you are looking for.

See http://www.tutorialspoint.com/computer_fundamentals/computer_quick_guide.htm

I suggest skipping the "Computer - Number System" and "Computer - Number Conversion" sections, and resuming at "Computer - Data and Information".

A good first read is the much shorter overview at http://www.bleepingcomputer.com/tutorials/introduction-to-your-computer/