Contractions are two words that are joined together like. Is not is now isn’t. The ‘ is placed when the letter was. Here are lots of examples.
It is, It’s. I am, I’m. He is, He’s. Would not, Wouldn’t. They will, They’ll.
I’ll do it but Sam wouldn’t and he’d just said no, they’ll do it but Jess didn’t like it even though she’d normally would.