REFRESH : If REFRESH is applied on an internal table then the entries in the table will be deleted but the memory allocated to that table still exists.
FREE : If FREE is applied on an internal table then the memory allocated to that table will not exist and that memory can be used by some other variable/object.In this case both the entries and the memory do not exist anymore.
FREE : If FREE is applied on an internal table then the memory allocated to that table will not exist and that memory can be used by some other variable/object.In this case both the entries and the memory do not exist anymore.