it, this and that

it

- pronoun

- used as the subject of a verb, or the object of a verb or preposition, to refer to a thing, animal, situation, or idea that has already been mentioned:

 

this

- determiner, pronoun

- used for a person, object, idea, etc. to show which one is referred to:

 

that

- determiner, pronoun

- used to refer to a person, object, idea, etc. that is separated from the speaker by space or time:

 

[출처] Cambridge Dictionary