Remember this rule:
- We use 'that' with singular and uncountable nouns;
- We use 'those' with plural nouns.
'That' and 'those' indicate and point to a person or object which is far from us (or it is not within our reach). This 'distance' can be physical and temporal, i.e. it can be related to the physical position of the thing or object or it can refer to the distance in time.
Normally, for introducing someone to another, we use 'this' or 'these'. We use 'that' or 'those' for introducing only when we are talking to someone about another person. For example:
See that girl over there?
Do you know any of
When describing two people or things in two different groups, we can use 'this/these and that/those' to differentiate between them. For example: