*We use (this) and (these) when the things are near.This goes with a singular or uncountable noun.But these goes with a plural noun.
EX:This girl is very beautiful.
EX:This water is too cold to drink it.
EX:These apples are good.
*We use that and those when the things are far from us.Not necessarily very far but what we can't touch it with our fingers.That goes with a singular or uncountable noun.But those goes with a plural noun.
EX:That furniture looks expensive.
EX:That book is about animals.
EX:Those books are mine.
*When we want to refer to a place where we are,we use (this ) not (that):
EX:This is a wonderful garden.(true)
*We can use this to introduce people and that to identify people.
EX:John,this is my friend Michael.
EX:That is Andrew over there.