While it may be a touch late to the free-to-play revolution, the industry-run Entertainment Software Rating Board (ESRB) recently posted a parent’s guide about free-to-play business models. While this is fairly well-trod territory for most MMORPG veterans, it’s a good overview that helps define F2P in the larger video game industry.

“Few things are truly free, and that goes for video games, too,” the guide says. “If you see a free-to-play game there’s a good chance it is a freemium experience supported by in-game purchases of some sort.”

The guide goes on to differentiate between “free” and “free-to-play,” noting that the latter tosses in microtransactions, battle passes, lockboxes, gacha mechanics, and paywalls. “Fortunately, games are required by most storefronts to display the probability for what can be obtained through loot boxes. These may be in the app itself, on the game’s product detail page, or on an official website,” the guide notes.

The ESRB says that it labels each game that has F2P purchases on the full rating information page for a particular title.