In yoga, it's important to have open, flexible hips for many poses. Unfortunately, some sequencing that focuses on hips can seem more like torture than like a soothing and enlightening experience. Most teachers teach Eka Pada Rajakapotasana (One-Legged King Pigeon Pose) or Baddha Konasana (Bound Angle Pose) to open the hips. These poses focus on the exterior hip muscles.
But Utkatasana (Chair Pose) and Parivrtta Janu Sirsasana (Revolved Head-to-Knee Forward Bend) can be effective hip openers, too. They also work the inner legs, deep muscles of the back, and hip flexors.