"Demonstratives" can be demonstrative pronouns, or they can be demonstrative adjectives.
This car is mine. "This" is a demonstrative adjective.
Whose car is this? "This" is a pronoun."
This tip briefly, and incompletely, discusses "demonstratives." https://www.duolingo.com/skill/cs/Masculine/tips-and-notes
IN English "this" would be a demonstrative PRONOUN, and not a noun. (A PROnoun substitutes for a noun.)
I assume the same is true in Czech (Namely, its a demonstrative pronoun.
This tip confirms what I say, I believe. https://www.duolingo.com/skill/cs/Masculine/tips-and-notes