Are the doublers inserts for the pocket diapers?

Are the doublers inserts for the pocket diapers?

Inserts and doublers are basically the same thing and can be made of a variety of fibers. Inserts are referred to as that when used in a pocket diaper because they can be "inserted," in an AIO they're just laid in so then they're called doublers. I sometimes fold a pre-fold and stuff that into a pocket diaper with an insert if I think I need some extra stuffing for a long car trip or
overnight, etc.