Subtle. :) The Beatles sang "Help, I need somebody / Help, not just anybody" - and that's the most general explanation: "somebody" (and other some- words) refers to an unknown/unspecified person, while "anybody" refers to *any* person - with a stronger accent on that part. For example, if you want to tell somebody something, you have a certain thing on mind, and when you want to tell somebody anything, you just want to talk to them, no matter what about. There are a lot more subtleties to that, and in some context the words can't be used interchangeably. Here's a good place to start: http://forum.wordreference.com/showthread.php?t=197248

Somewhere- In or at a place having a position that is not stated or not known. Example: He was last heard of living somewhere on the south coast. Anywhere- (1) In, to, or at any place: (2) Used in questions or negatives to mean 'a place': Example (1): Go anywhere in the world and you'll find some sort of hamburger restaurant. Example (2): I can't find my keys anywhere. Somebody (or someone)- Used to refer to a single person when you do not know who they are or when it is not important who they are. Example: Somebody must have seen what happened. Anybody (or anyone)- Used in questions and negatives to mean 'a person or people'. Example: Was there anyone you knew at the meeting?