Say the word “meme” and most people think of funny videos that go viral or assaults by internet trolls on platforms like 4chan, a website frequented by alt-right groups. President Trump, who regularly retweets memes, many of them directed at Democrats, is perhaps the most famous devotee of the form.

Memes are powerful tools for communicating ideas, a fact Mr. Trump seems to understand better than many of his critics. One needs only to look at the reach of the Russian government’s memes to understand why it exploited the form in trying to influence the 2016 election.

The term “meme” was first coined by the evolutionary biologist Richard Dawkins in his book “The Selfish Gene.” Successful memes, he believed, had common elements: They were long-lived and could be copied easily and disseminated widely. The rate at which memes were created increased exponentially with the advent of the internet and social media.

Internet memes typically combine text with images or video, often humorous in nature. And because video is rich in information, it makes memes particularly effective in conveying snappy ideas, such as political expressions like “fake news” or mocking nicknames like “Crooked Hillary” or “the Amazon Washington Post” favored by the president.