Minutes before turning his van onto a Toronto sidewalk on Monday, killing 10 people and injuring more than a dozen others, Alek Minassian wrote a post on Facebook, according to the Canadian authorities.

In it, he praised Elliot Rodger, who in 2014 shot and killed six people in Isla Vista, Calif. Mr. Minassian, 25, also wrote of an “incel rebellion,” referring to a term, shorthand for “involuntary celibates,” used online by a community of misogynists to describe themselves.

“The Incel Rebellion has already begun!” the posting read. “We will overthrow all the Chads and Stacys! All hail Supreme Gentleman Elliot Rodger!”

Here’s a brief guide to the incel community, including some of the coded language, such as “Chads” and “Stacys,” used by its members.