ASANA
Wide Leg Forward Bend - Prasarita Padotanasana
Back body stretch and spinal flexion

This is one of the foundational standing poses and is a good rest relative to many of the other more demanding standing poses, so it often comes between sets of other standing poses or as a last standing pose before moving to something else. It also makes an interesting transition to tripod headstand and handstand. Wide Leg Forward Bend works eccentric contraction of the hamstrings and adductor magnus muscles as you move into the fold. Adductor Magnus gets stretch from both the forward bend as it assist in hip extension and the hip abduction. It's a good pose to start working on wide leg positions for beginners. 

Technique

Plant the feet wider than the hips and turn the toes slightly inwards. Less mobile people can bend the knees initially. As range increases you may find it biomechanically integrative to work with straight legs and co-activating the thigh muscles as if reaching through the legs. The hands can be placed in a variety of positions that give different work to the upper body to assist the forward bend or move to deeper flexion for the spine.