Camel Pose
Also: Ustrasana
Stand on your knees, with the tops of your feet and front of the calves parallel on the floor behind, ideally at shoulder width. Keeping the thighs as close to vertical as possible, arch the back to bring the ribcage parallel eight the floor. Hands grasp their respective ankles. The neck usually continues the curve. The ribcage and calves are the short ends of a rectangle.
One progression of the pose brings the elbows to the ankles, one of several ways to enter a triple fold.
Camel twist
Also: contortion twist, knee bridge twist
From the camel pose, hands are switched to their opposite ankles, the arms crossing. The arms are then straightened - temporarily bending them at the elbow - back to parallel by performing a torso twist, without releasing grip on the ankle. The front of the ribcage is brought parallel to the floor instead of the back of it. This motion usually leaves the pelvis out of line with the head and knees, depending on the performer's ability.
If this is done without knees touching the ground, it is a Crab Walk and crab twist.