This is a demonstrative pronoun. That is a demonstrative pronoun. These and those are demonstrative pronouns.
So what the heck is a demonstrative pronoun?
A demonstrative pronoun is a pronoun which identifies a noun in space and/or time.
Examples of demonstrative pronouns are this, that, these, and those. When these are combined with an actual noun, they become demonstrative adjectives. (Compare "this" with "this dog.")
This and these refer to things close to the user in space and or time. "This writeup", "these nodes", etc.
Conversely, that and those refer to things far away. "That upvote", "those Chings!", etc.
In some languages (note: not English) there is an additional distinction between things far away from the speaker but close to the receiver ("that pencil on your desk") and things far away from both speaker and receiver ("that star in the sky.")
Perhaps the most famous use of demonstrative pronouns is in the 1978 movie The Deer Hunter, in which Robert DeNiro's character explains to his friend (played by John Cazale): "This is this. This is not something else. This is this."