Ahhh, but do YOU think you should learn, do you really feel the need to understand it...If yes, then go for it, there's plenty of sites online which can help, you could go ask your music teacher in school, try and teach yourself, whatever...
If it's no, then don't worry about, if you can still play the things yuo want, THAT'S what's really important...Think about what you want to get out of music...