Yoga Term: ??
This pose is close to the Pigeon pose of Yoga. The only difference is the foot is moved forward to a 90 degree angle to the center of the body. This is a great pose for stretching the area of the hip above the joint to the sacrum and the glutes of that side. As I have shown above are beginner to advanced variations. The areas of the stretch -at least on me- can be very tight. This can be true for most people, especially those that walk and stand with their feet turned out.
Alignment points:
Hips are squared to the front of the room. Place the forward foot slightly outside the line of your body and center yourself perpendicularly with your lower leg. Place your hands in front of that leg at about the width of your knee and ankle. The other is straight back from the hip where you feel it is most comfortable. Keep that leg relaxed with the toes pointed back. Just focus on relaxing the hip until you can come to the floor eventually bringing the lower leg to the chest.