somebody and anybody, something and anything, etc

The difference between somebody and anybody, someone and anyone, somewhere and anywhere, something and anything is the same as the difference between some and any. Most important, we use somebody etc in affirmative clauses, and anybody etc usually in questions and negatives.

    There’s somebody at the door.
    Did anyone telephone?
    I don’t think anybody telephoned.
    Let’s go somewhere nice for dinner.
    Do you know anywhere nice?
    I don’t want to go anywhere too expensive.

Somebody, something, anybody and anything are singular. Compare:

    There Is somebody waiting to see you.
    There are some people waiting to see you.