Memes are defined as units of cultural inheritance that transmit ideas or behaviors through imitation and symbolic communication, akin to a viral propagation mechanism. Richard Dawkins popularized the concept in his book 'The Selfish Gene,' linking memes to natural selection and suggesting they survive in a 'belief pool' similar to genetic competition. Memetics, the study of ideational transmission, remains controversial, with varying opinions on its implications for free will and religion.