A red herring is a dried, smoked, herring. The curing process turns the fish red.

In former times, a fugitive would reputedly drag a red herring across his trail so that its odor would cause the dogs pursuing him to lose his scent and follow the herring odor instead. This practice has led to a number of related metaphorical senses of red herring, sharing the general sense of assigning more than warranted importance to something with little actual significance:

• a type of logical fallacy in which one purports to prove one's point by means of irrelevant arguments. See Ignoratio elenchi.
• in detective work, mystery fiction, and puzzle-solving, a false clue which leads investigators, readers, or solvers towards an incorrect solution
• in politics, a minor or even phony issue trumped up as being of great importance, in order to influence voters to vote for one party or candidate and against the other, or distract from more important issues that might help the opposing party.
• in literature, a plot device intended to distract the reader from a more important event in the plot, usually a twist ending
• in adventure games, an item or object of no practical use; its purpose to frustrate the ignorant gamer who tries to find the intended use for it. A famous example is the chainsaw of Maniac Mansion.

Other

• in finance, a preliminary prospectus for an offering of stock, so called for the notice in red type required by law at the top of the front page
• a brief for venture capitalists to tempt them into following up with investment in the business plan
• "Red Herring" Is an artists collective based in Brighton on the south coast of England founded in 1984, seen as one of the pioneers of the establishment of artist run studio organisations in Great Britain
• Red Herring, a business magazine founded in the dot-com boom of the 1990s, when venture capitalists and business plans abounded.
• in Tasmania it is a brand of Surfgear