A meme is a contagious idea. Viral images overlayed with text are often referred to as "memes," despite being a subset of all memes.
The term "meme," in its current usage, originated with Richard Dawkin's 1976 book, The Selfish Gene. The term has increased in popularity during the Internet age.
Commonalities of Memes
Memes tend to be primarily rhetorical devices, as rhetoric is known to be the best mechanism for persuasion. While many are derived from movie quotes or funny turns of phrase (thus, designed primarily for amusement), others are carefully phrased citations of poignant facts.
A meme is considered to have failed when it does not become viral or does not create the intended persuasive effect. "White genocide," for example, is a failed meme primarily because people associate genocide with piles of corpses instead of cultural destruction. In a different way, "Gamers are over" was a failed meme because it prompted extreme negative reaction and a host of memes related to the movement known as Gamergate.
Examples of non-image memes:
Examples of image memes: