pronoun
a few, a couple
A2
paar means 'a few' or 'a couple' (indefinite quantity). Lowercase 'paar' is an indeclinable indefinite pronoun/adjective (ein paar Bücher). Capitalized 'Paar' is a noun meaning 'pair' (two items). No special preposition. Usage: often with plural nouns; context decides exact quantity.
Examples
Er brachte nur ein paar Bücher mit, weil er kaum Platz im Auto gehabt hatte.
He only brought a few books because he had hardly any space in the car.
Wir gehen in ein paar Minuten los.
We'll leave in a couple of minutes.
Ich habe nur ein paar Fragen.
I only have a few questions.
Details
Mnemonics
imagine two matching socks — a small 'paar'
sounds like English 'pair' (two)
Notes
As an indefinite pronoun, 'paar' is used without an article in plural meanings ('ein paar' = some/a few).