The name, Marichi's pose, comes from the fact that the pose is dedicated to the sage, Marichi, from Hindu mythology who is also the son of Brahma.
Marichi's pose A provides a powerful stretch for the spine and shoulders. It can also increase flexibility in the hips and hamstrings. It has many internal physical benefits as it massages the organs and glands. It is said to improve digestion, breathing and may relieve menstrual pain.
This pose can be challenging if the groin is tight because it can be hard to keep the thigh of the bent leg pressed into the side of the body. It is helpful to have a partner or teacher squeeze the torso and thigh together as you learn to enter this posture. It can also be modified by holding a strap between the hands if they cannot reach far enough to clasp each other. Sitting on a folded blanket can also help by lifting the hips.