"Leak site" is the common term for a website that republishes content creators sell behind a paywall, or share privately, without their permission. Some collect content uploaded by users, some organise it by creator name, and some are forums or file hosts where links to the content are shared. Telegram channels and Discord servers can play a similar role.
These sites usually make money from advertising, paid memberships, or donations, which gives operators a reason to keep content up. Many are run anonymously, sit behind privacy and proxy services, and move to new domains when they come under pressure. That's why removal often means going beyond the site itself: to its hosting provider, and to search engines so the pages stop appearing in results.
For creators, the practical steps are the same wherever content ends up: document the URLs, file DMCA notices with the site and its host, request Google de-indexing, and keep monitoring for re-uploads. Privly does this for creators, filing as a registered DMCA agent so your legal name stays off the notices.