Indifenite Pronoun

An indefinite pronoun is a pronoun that refers to non-specific beings, objects, or places.

Indefinite pronouns can represent either count nouns or noncount nouns and include a number of sub-categories: universal (such as everyone, everything), assertive existential (such as somebody, something), elective existential (such as anyone,anything), and negative (such as nobody, nothing).^[1]

They are associated with indefinite determiners (sometimes called indefinite adjectives) of a similar (or identical) form (such as every, any, all, some). A pronoun can be thought of as replacing a noun phrase, while a determiner introduces a noun phrase and precedes any adjectives that modify the noun. Thus all is an indefinite determiner in "all good boys deserves favour" but a pronoun in "all are happy".

http://en.wikipedia.org/wiki/Indefinite_pronoun