For a table 'a' that contains another table 'b'; when copy is done on 'a' an entirely new copy of 'a' is created. However the objects contained in the table are not duplicated; so both 'a' and the copy of 'a' contain the table 'b'. Thus, if a change is made to the table 'b' in 'a', that change will show up in the copy of 'a' as well, and vice versa.
For a list of records, deep must be used to obtain unique instances of the records.