Use of This, That, These, Those

This, that , these and those are demonstrative pronouns. 

• We use this, that, these and those to point to people and things.
• This and that are singular.
• These and those are plural. 
• They also indicate whether the object is close or far from the speaker at the time of speaking.

The (singular) and these (plural)

We use both of them to talk about people and things near to us e.g. 

- This is a nice dress.

- This is not my bag.

- This is a good idea.

- Whose books are these?

- These are my friends, Vikas and Madhu.

The (singular) and those (plural)

We use both of them to indicate people or things that are not near us e.g.

- That is my school.

- Those are expensive dresses.

- That is not your bag.

- That guy looks weird.

- That is a delicious ice-cream.

- Those are not his books.

- I cannot join that university.

- She has won this prize.