Besides the fact that in normal discourse a herring is a fish, in logic and literature, a red herring is a fallacy of relevance – a clue or piece of information that is (intended to be) misleading, and diverts attention from a question or piece of relevant evidence.
A red herring is the author’s way of sending his audience on a wild goose chase.
Consider detective novelist Agatha Christie, inventor of Miss Marple and Hercule Poirot. Difficult clues and red herrings were her most powerful devices for misleading and confusing the reader. The key to solving a complex Christie-style murder plot is to determine what is a real red herring and gather enough clues.