The word meme was coined by the biologist Richard Dawkins in his 1976 book The Selfish Gene, in which he suggested that ideas could replicate, evolve, and enter popular culture in a process analogous to the way genes spread. Today, a meme is commonly thought of as a variant of an image based on a common theme that has spread widely on the internet. Memes are often humorous or ironic, but they are also vehicles for political messages, used to spread aggressive or racist messages and to incite hatred.
Several online communities focus on creating and spreading memes with the goal of making an idea become viral—a process known as “attention hacking” or “weaponizing.” These communities, on websites such as Reddit, 4chan, Twitter, and others, have become hugely influential.
In other words, /pol/ is a shit-filled sewer of garbage, /r/the_donald is the scum floating on top of said sewer and all the racist idiots are where you expect them to be.