When we want to point at some object or a person, we say this/that + noun.
Which word to use, depends on how far this object/person is from us.
This / these → here
When an object (a person or a thing) is very close to us, we can reach it and touch it, we use the words this and these to point at it.
"This" is for singular and "these" is for plural.
This is for you.
What is this? This is a self-balancing scooter.
These are my friends.
Who is this?
These trees are maples.
That / those → there
When an object is not close, we can't touch it, we use the words that and those to point at it.
"That" is for singular and "those" is for plural.
Look at that river!
Is that a gas station over there?
Whose are those cups on the table?
In a dialogue, when we react to what the other person says, we use "that" not to repeat the thought.
A: Are you an accountant? B: Yes, that's right. = Yes, you are right: I'm an accountant.
A: Sorry, I'm late. B: That's not your fault. = It's not your fault that you're late.
A: I'm on holiday in Italy now. B: That's great! I'm happy for you. = It's great that you are on holiday in Italy.