Use indefinite pronouns, like everybody, to refer to people or things that are not specified. Indefinite pronouns ending with –body refer to people:

Everybody

Somebody

Anybody

Nobody

Indefinite pronouns ending with –thing refer to things:

Everything

Something

Anything

Nothing

Indefinite pronouns ending with -one mean the same as indefinite pronouns ending with -body:

everybody / everyone

somebody / someone

anybody / anyone

nobody / no one

Note that the verb takes the 3rd person s-ending after indefinite pronouns:

Nobody in our group knows how to play darts.

Every, some, any, and no can also be used independently as adjectives before a noun, e.g.:

Every child

Some woman

Any idea

No man