- (auxiliary) (linking) The contracted form of is.
- She's right.
- (auxiliary) The contracted form of has.
- She's gone to the store.
- (informal) (auxiliary) THe contracted form of does
- What's he doing?
In the US and other places, they only use the contraction 's when the word 'has' is helping another verb go into the perfect aspect.
- The contracted form of us, but only in the word let's, which you say if you want a group of people you are with to do something.
- Let's go to the store; I'm so hungry!