How to use "ain't"? as well as something related t

1, I'm not= I ain't ? But I heard of the usage of " You ain't......"
Too weird, how to use this word? And is it only used in oral English?

Thanks, I'm expecting your answers.

2, I usually learn some slangs or word usage related to sex or male's.... You know. ( I don't mind to say that but i don't know about you.)

In american movies I can easily see or hear that you guys speak out such words in the public. Is it a real situation? You won't think such people are kinda gross? Xixi, like F word. which is the first English word I'd really like to speak when I was young. I think it's pretty cool at that time.

[RonBee]

The word ain't is used (especially in informal conversation), but it is frowned on by those whose job it is to frown on such things (grammarians and schoolteachers).

Say slang for both the singular and the plural.

The word fuck is not used in polite society, but it is used. It is certainly possible to get by withiout it. Some use it a great deal, others not at all.

:)