It really depends on which grammar book's terminology you want to follow. The two sets of terms are closely related to each other. Let's suppose "you" refers to somebody named John. Both "your" and "yours" are then equivalent to "John's." Both are possessive forms, just as "John's" is a possessive form.
Which to use depends on whether the possessive is followed by the thing possessed ("John's car" --> "your car") or whether the thing possessed is elided ("The car is John's" --> "The car is yours"). We can't say, *"The car is your." When there is noun phrase ellipsis following the possessive pronoun "your" ("your" is equivalent to "you's"), it's pronounced "yours."
As you can see, I use "possessive pronoun" for both types.
Quirk et al. (1985, A Comprehensive Grammar of the English Language) refer to "my"/"her"/"our"/etc. as possessive pronouns (see Section 6.29, p. 361). They also refer to "mine"/"hers"/"ours"/etc. as possessive pronouns. The difference is that they call the first set "determinative possessive pronouns," and the second "independent possessive pronouns."
Huddleston & Pullum (2002, The Cambridge Grammar of the English Language) call them "dependent genetives" and "independent genitives." They write, "The dependent and independent genitives are often analyzed in traditional grammar as 'possessive adjectives' and 'possessive pronouns' respectively, but we find this an unsatisfactory way of handling the difference" (p. 361).
The problem is that a lot of Internet resources and even some textbooks make no distinction between them whatever, and lump them all under one term, whatever that may be.
I find that vexing, as it misleads students into thinking they can all be used the same way in a sentence. It's already confusing for learners what with the third person masculine and neuter being recycled.
So, I get frequent "That car is my' and "Which is yours car" types of errors.