Good explanation of cascade (ON DELETE/UPDATE) behavior
If you like the Parent and Child terms and you feel they are easy to be remembered, you may like the translation of ON DELETE CASCADE to Leave No Orphans!

Which means that when a Parent row is deleted (killed), no orphan row should stay alive in the Child table. All children of the parent row are killed (deleted), too. If any of these children has grandchildren (in another table through another foreign key) and there is ON DELETE CASCADE defined, these should be killed, too (and all descendants, as long as there is a cascade effect defined.)

The FOREIGN KEY constraint itself could also be described as Allow No Orphans! (in the first place). No Child should ever be allowed (written) in the child table if it hasn't a Parent (a row in the parent table).

For consistency, the ON DELETE RESTRICT can be translated to the (less aggresive) You Can't Kill Parents! Only childless rows can be killed (deleted.)