Feature flags
A feature flag is a switch inside your product that turns part of it on or off for its users. You set your product's flags, and its applications read them.
Description
The hub has flags of its own too, which gate the hub itself: whether new people may sign up, whether sign-in by email is on, whether sign-in with GitHub is on, and others. Those belong to the admin workspace, not to a product.
A product's flag can also gate part of what the hub does for that product. Messaging has to be switched on before direct messages work.
Tech Detail
The stack of Ecosystems and products