Why can't anyone say it? Generally, the "N" word refers to the racial slur "nigger." This is a highly offensive term for a black person and it shouldn't be said by anyone. I would like to see it completely stricken from the world's lexicon but it won't happen. Since the OP asked what it meant, I am telling him/her. I would rather this person, who may not be American, know what the word is and means so they don't go around thinking it's acceptable to use.
Why is it that black people call each other the "N" word all the time, but everyone freaks out when a white person says it? Words only hold the power we give them. This society needs to grow up and stop being afraid of things for no reason.
It's a racially demeaning term. Some people think it's cool to throw around that term lightly. They don't realize it but they are disrespecting themselves and each other and teaching others to do the same. You can't demand respect of others when you don't first respect yourself.