You use those to refer to people or things which have already been mentioned.

You use those when you are referring to people or things that are a distance away from you in position or time, especially when you indicate or point to them.

You use those to refer to someone or something when you are going to give details or information about them.

You use those to introduce more information about something already mentioned, instead of repeating the noun which refers to it.

You use those to mean 'people'.

You use those when you refer to things that you expect the person you are talking to to know about or when you are checking that you are both thinking of the same people or things.