"Meme" is a term a transmissible unit of cultural information. Especially one that can be passed from mind to mind verbally, by repeated actions, or through general cultural transmission. Religions are memes. So are fashions and bodily adornment. Or popular sayings or slogans or tunes or fads in entertainment or advertising. Memes tend to pass from person to person or group to group like a virus.

In 1976, the biologist Richard Dawkins coined the term meme in the course of a popularized discussion of evolutionary theory. According to Dawkins, a meme was a unit of cultural information – an idea, a fashion, or a technique. Dawkins made a deliberate analogy to the concept of the gene as a unit of biological information. He proposed that it might
be useful to think of ideas as subject to laws analogous to those governing organisms. Ideas copied themselves from one human mind to another, just as biological organisms copied themselves through the natural reproductive process. Ideas could spread through a human population, much like a virus. Ideas, like genes, were subject to mutation. Ideas competed for the attention of human beings, just as organisms competed for energy and the chance to mate.
Dawkins' proposal was slow to have any effect in the scientific community. Over the course of the 21st century, memetics has developed into a hybrid of neurobiology and mass psychology. Memeticists study how the human brain generates and stores ideas, and how ideas are likely to change as humans share them with each other. A few practical results have appeared, advancing the state of fields such as cognitive science, demographics and psychology. No stunning breakthroughs have been made.
The primary influence of memetics has been in popular culture. One implication of the meme concept is that all elements of human culture are essentially artificial. An idea can survive and spread because it is good at attracting human attention – and this "talent" may have nothing to do with the idea's truth. People who follow pop-science memetics tend to treat all ideas as conditional, not worth accepting without question. This tends to infuriate followers of various religions, political ideologies, and other beliefs requiring a commitment of faith.
Memetics also encourages one to think of his own beliefs as foreign ideas that have gained a foothold in his mind. As a result, a follower of pop-science memetics may decide to "have his memes upgraded," just as he might undergo genetic therapy or have biotech devices implanted. The popularity of memetic ideas has thus led to a surge in demand for psychotherapy, making the therapeutic industry a significant sector of the economy in some First World nations.