If I knew what the cross apply operator was

If they want the word its join, a description could be "the Cartesian product of multiplying the tables" and an example would be "like merging two matrices except every column may be of incongruent variables creating a result with polynomial rows, (which is likely no longer normalized to the form level of the database)"

An Apply operator is a join type that the query engine evaluates in sequential order because the right-hand table object can reference data in the left-hand table object. The Cross Apply operator is the Apply operator that acts like an Inner Join, eliminating any records in the left-hand table object that have a null match in the right-hand table object.

An Apply operator is a join type that the DB engine evaluates in sequential order because the right-hand table object can reference data in the left-hand table object. The Cross Apply operator is the Apply operator that acts like an Inner Join, eliminating any records in the left-hand table object that have a null match in the right-hand table object.