Bokutachi/Watashi-tachi
 

I hear in a lot of anime and Japanese songs. I know that both of them means "we", but what is the difference between the two? At first, I thought that only boys use 'bokutachi' but in a lot of Japanese songs sung by girls, they use 'bokutachi' also....(Example: Every Heart by BoA)

Anyone can tell me the difference? ^_^;;

Also, is 'kimi' and informal way of saying "you"?

Songs are like poems, and the rules go out the window...

Bokutachi is generally a term used by men, but occasionally you'll hear a girl use it.

Kimi is an informal way of saying, "you", so should only be used with close friends, and not used at all if unneeded.