The explanations in here are correct, but another very important one that hasnt come up is the candidacy program. After a fairly lengthy onboarding process, members are brought in on a provisional status called "candidacy". That lasts about a year and is a focused period of training on Marxism, history, political analysis, rhetoric, and a ton of practical organizing skills. That includes a nine-month biweekly class deep diving into subjects like the USSR, national liberation, the PRC, and the history of revolutionary movements in the US. By the time someone finishes candidacy, they should be a well trained and educated revolutionary committed to our political line.