It is quite a big class of nouns - "adjectival nouns".
They are derived from adjectives, and morphologically behave as adjectives (i.e., they keep adjectival endings in all their forms).
But syntactically (i.e. in terms of sentence-construction) they are nouns.

There are many examples in addition to what was mentioned above:
столовая - dining-room;
парикмахерская - barber's shop;
русский (русская) - a Russian (man or woman) - it can be used both as an adjective and as a noun;
животное - animal;
насекомое - insect;
Вселенная - Universe;
прохожий - a passer-by;
часовой - a sentry

etc. etc.

BTW, many Russian family names are of this sort: Лев Толстой (compare: Я читаю Льва Толстого).