Hi Stuart, apologies on the naming conventions I wasn’t sure how deep you were into learning all of the WiX/Velo features.
Content collections are where you store any content related data. WiX apps (like bookings that you are using) automatically adds some of these tables, but you can add your own.
The Data API is how you will then query (there are backend and FE APIs available and depending on your approach you will want to decide where to put your queries)
Also make sure to read about permissions when creating a new collection. The collections added by the bookings app come configured (some can be modified), but when you create your own you will want to make sure to asses who should have permission to access the data.
Some reading…
Content Collections
Wix Data API
Content Collection Permissions
edit: also, i cleaned up our conversation to make it easier for anyone passing through to see how to do this and focus on what Jacob stated as he knows bookings much better than I do