This is a variation of Bridge pose (Setu Bandha Sarvangasana), with one leg raised to the sky. The full Sanskrit name for this posture is Eka Pada Setu Bandha Sarvangasana.
Along with all of the benefits of Bridge Pose this variation additionally strengthens the upraised leg and buttocks.
Placing a block under the foot increases the angle of the body, adding a layer of difficulty to the pose.
Modified One-Legged Bridge with Block: How to Do it Step-by-Step
Tip: Keep the chin slightly tucked into the chest to protect the neck.