All yoga styles fall under the same blanket term of yoga, but in terms of their energy, they can be divided into two categories: Yang forms of yoga are active, whereas yin forms are more passive.
Styles like ashtanga, vinyasa, and power yoga are obviously yang, as they quickly flow from movement to movement.
On the opposite end of the spectrum is yin yoga. In a yin practice, poses are usually held for up to 20 minutes (Beginner or Intermediate Yin will only hold poses at most 8 minutes). Poses are held for longer periods of time to work on the deeper components of the physical body: connective tissue, ligaments, tendons, fascia, and even the bones. The long holds also foster an inner stillness that lends itself to a meditative practice.