This is the 31st most frequent Polish word.
osób
"Osób" means "persons" or "people" in its genitive plural form.
The word 'osób' is the genitive plural form of 'osoba' (person) and is used here to indicate the number of people the room can accommodate.
W tej sali jest miejsce dla dziesięciu osób.
This room accommodates ten people.
'Osób' is used in the genitive case to describe an unspecified group of people I haven't met.
Nie znam tych osób, ale wyglądają na sympatycznych.
I don't know these people, but they look friendly.
Here, 'osób' appears in the genitive plural again, indicating for whom the offer is targeted.