The 3Doodler is the world's first 3D printing pen that allows users to "draw" in the air or on surfaces using plastic filaments. It contains an electric heater that melts the plastic, which is then extruded through the pen nozzle. Users can control the extrusion speed and draw continuously by double clicking. The pen is easy to use but does have some limitations like not adhering to all surfaces and potential for jamming. It can be used to create 3D shapes, jewelry, art, and other crafts.