"Collections" stores a single records table meta data (eg. name, fields, validators, etc.), so when you create a new collection a new related table will be created (see https://github.com/pocketbase/pocketbase/blob/3d07f0211dc747...).

The admin UI just shows the collections through the web api (https://pocketbase.io/docs/api-collections/).

I actually started with GORM, but its too complex and I ended up replacing it with a simpler query builder package (ozzo-dbx). While the query builder has abstraction for other databases, I'm not planning supporting them at the moment.