This and That are for singular nouns.
This is used for an object which are near to use
example: This is my pen in my hand.
That is used for an an object which is not near to us.
example: That is my bag you are carrying.
These and Those are for plural nouns.
These are used for objects which are near to use.
example: These are my new shoes I'm wearing.
Those are used for objects which are not near to use.
example: Those were my co-workers at the meeting.