What are memes?

A meme (rhymes with "dream", but comes from memetic and memory) is a unit of information that replicates from brains or stores of information such as books to other brains or stores of information. A smiley exemplifies what some might consider a visual meme. Anyone who has seen a smiley can copy, reproduce, or modify it and then show it to others.

In more specific terms, a meme is a self-propagating unit of cultural evolution, analogous to the gene (the unit of genetics). The term was coined in 1976 by Richard Dawkins in his controversial bestselling book "The Selfish Gene". Memes can represent parts of ideas, languages, tunes, designs, skills, moral and aesthetic values and anything else that is commonly learned and passed on to others as a unit.

In casual use, the term meme is sometimes used to mean any piece of information passed from one mind to another. Memes on the internet tend to proliferate for periods of time then quietly die off, and many start as obscure running jokes within net cliques which gradually lose their original meaning or otherwise become detached.

(source: Wikipedia)