A dab pen is a vaporizer pen specifically designed to vape cannabis concentrates. A regular dab pen comes with atomizers, coils for heating the material and mouthpiece, which you inhale through to get the vapor.
A dab pen is something which is used purely for the consumption of dabs. Dabs are tiny little concentrates of THC, instead of your more traditional dry herb or e-liquid. There are so many different ways to consume cannabis—joint, blunt, pipe, bong, vape, dab, etc. —because the way you consume directly impacts the experience. A dab pen is made up of the same components as a vape pen, and works more or less in the same way.
The dabs placed into a dab pen should be of a thin enough consistency that it can be heated to vaporisation point without combusting (burning). The dabs are placed directly onto the coils and heated so it melts down onto a wick which then absorbs the product. The wick then heats up the material to create a vapour which is then inhaled.