The below is from an article I found on the Mayo News site. Please follow the link below to get a detailed description of how to do this pose and to see a picture of the pose preformed correctly!
Padangusthasana, or ‘big toe pose’, has many benefits. It calms the brain and helps relieve stress and anxiety, stimulates the liver and kidneys, gives the hamstrings and calves a good stretch, strengthens the thighs, improves digestion, helps with the symptoms of menopause and relieves headache and insomnia. However, if you have lower back or neck injuries, it’s best to avoid this pose. The Mayo News - HEALTH: A yoga pose for stress, headache and insomnia