Hello,
'This'
is a demonstrative pronoun indicating a singular place, direction, person, or thing; either spatially or figuratively. They have to be present or near in place or time.
'These'
It is the plural form of 'this' ,so it refers to the same things near in place or time but in plural form.
'Those'
is the plural form of the demonstrative pronoun 'That'.
It also refers to things or persons, that were previously mentioned or far in place or time.
'That' as a relative pronoun differs from 'that' as a demonstrative one 'that ,those' .
The relative pronoun 'that' is equivalent to 'which' and points out a person or a thing spoken of before in a sentence and may be both singular or plural.
"This is the place, that I told you about."
'Which' is the same as 'that':
"These are the references, which you can use to write your thesis."