The biped feet can be in one of four states: touch, plant, lift, and move. The general rollout displays foot states.
Plant: The biped foot state in full contact with the footstep.
Lift: The biped foot state just before leaving a footstep.
Move: the biped foot state between footsteps; an airborne period.
Touch: The biped foot state at which a biped foot first contacts a footstep.