Well, ok, that makes sense; I thought the OP was trying to say that AV provides protection against brand new zero-day exploits which seems like wishful thinking.
No, I meant basically what jgmmo said, the AV scanners pick up a lot more than the virus they were written to prevent. Anything that triggers virus-like behavior will let you know you're infected (might not be able to clean it though). That's one of the points made in the article about false positives.
