I bought some KASA switches to replace simple wall switches and have a question.

These switches have green, white and black wires protruding out of the bottom with two terminals on one side (both are marked Traveler).

Im not sure how this gets wired up. On my old switch, there's one black wire to the line (light bulb), one black wire to the load side (from the panel), one white (neutral) and one green (ground).

The green and neutral are logical, but what am I to connect the black wire coming out of the bottom of the switch to?