Many to many graphql index

Hi there!
What is the purpose of the third automatically created index in a many to many graphql relationship?
Cf relationships page, m to m relation, many users to many cars.
Thanks really much

For a many-to-many relationship between the types A and B, one index is for searching A, one index is for searching B, and the third index is for searching the relationship(s) between A and B.

See: GraphQL relations | Fauna Documentation

I got it.
Like gimme all the times Driver A drove car B.
Ok thanks