Apparently the digital perm makes it so that when you air dry your hair, your hair goes from slightly wavy to big and round. Exactly like if you were to curl your hair with a curling iron.
Only most Asian salons will perform this service. They wrap your hair in some metal perm rods and then hook up this machine to the perm rods to heat them up while apply perm solution on the rods.
A spiral perm or ordinary perm you can get at any salon is like the photo on the right. It is wrapped with rods and then a perming solution is applied. You wait, and then rinse when it is done processing. This procedure causes your hair to have more frizz and is more damaging than the digital perm.
But keep in mind that both perms are very damaging and not anyone can get one. If you have pre lightened hair (bleached/highlighte) you cannot receive a perm. It will overprocess your hair and you will get breakage.
Digital perm Normal Perm