English definition of “that”
A1 used to mean something that has already been talked about or seen: That looks heavy.
A1 used to mean something that is not near you: What’s that in the corner?
A2 used to make a connection with an earlier statement: My train was cancelled. That’s why I’m late.
that’s it › used to say that something is correct: You need to push the two pieces together. That’s it.