Last week, a trolling campaign organized by right-wing internet users spilled over onto Twitter. The campaign, which was born in the fever swamps of 4chan and Reddit message boards, involved creating hundreds of fictional personas with gray cartoon avatars, known as NPCs. These accounts posed as liberal activists and were used to spread — among other things — false information about November’s midterm elections.

Over the weekend, Twitter responded by suspending about 1,500 accounts associated with the NPC trolling campaign. The accounts violated Twitter’s rules against “intentionally misleading election-related content,” according to a person familiar with the company’s enforcement process . The person, who would speak only anonymously, was not authorized to discuss the decision.

If you’re confused, you’re not alone. Here, we try to unpack the NPC meme, what it means and why it’s causing trouble on Twitter.

What is an NPC?

NPC means “nonplayable character” or “nonplayer character.” It’s a term, borrowed from the world of video games, for a character that is controlled by the computer rather than by a player. An NPC often advances the game’s plot by saying scripted lines, or assisting the playable characters in some way.