This is a great pose for strengthening the legs and ankles. It also stretches the back of the legs, and strengthens the abdominals. It's a two part stretch - on the first inhale, you'll lift the right leg up straight out in front of you, and on the next inhale you take the leg out to the side and gaze in the opposite direction. It's not an easy pose, especially if you've got tight hamstrings. If this is the case for you, just bend the lifted leg and hold the knee instead of the big toe and practice it that way until you find the flexibility in the hamstring to extend the leg. Hope this helps!