Settings → API, titled Channel API.
This is for connecting another system to Glovebox — a booking agent, a broker, or software you have written yourself — so it can check availability and create bookings.
Most operators never open this screen, and nothing about running your business day to day needs it.
If you are connecting something, this is where the credentials live. Whoever is doing the integration will know what to do with them; if they need more than the screen offers, get in touch.