A Dib Dab is a package of sherbet powder sold with a lollipop.
You lick the lollipop, dip it in the powder and use that to carry it to the mouth.
The brand called Dip Dabs is made by Barrat; the brand called Dib Dab is made by Swizzels Matlow.
See Barrat Sherbet Fountains for information on the Barrat company.