They’re is a contraction that is defined as they are.
An example of they’re is what you say when expecting guests and the doorbell rings, “They’re here.”
Contraction of they are.
- Go over that way, they're there.
- They're gone for good.
- I suppose they're both a little artificial.
- They're not going to kick us out.
- I guess they're not as tame as they look.