Apostrophe:

It is a punctuation mark(') used:

with nouns to indicate that a thing or person belongs to somebody:

My friend’s brother

The waitress’s apron

King Jameel’s crown

The student’s hooks

The women’s coats

in short, forms, to indicate that letters or figures have been omitted:

I’m (am)

They’d (they had/they would)

The summer of ’89 (1989)