node - a file or folder in Google Drive, whose permissions we are interested in
assigned permissions - the permissions directly assigned to the node
effective permissions - the actual permissions used by Drive to determine access to the node
In determining a node's effective permissions, Drive determines which has more recently changed:
- The assigned permissions of the node
- The assigned permissions of the node's parent folder
If #1, then the node's effective permissions are its assigned permissions.
If #2, then the node's effective permissions are its parent folder's effective permissions.
Observe that this makes the definition recursive, and you start to realize how complicated this actually is.
I'm pretty confident of this after doing quite a bit of experimenting, but please correct me if there's more to it than this.