The Tadasana posture is also called the Mountain posture. It is a basic standing posture with the feet together (big toes touching and heels slightly apart) and the hands at the sides of the body.
While in the mountain pose keep the spine long and spread the body weight evenly across the feet. Keep the abdomen, knees and thighs firm without locking the knees or hardening the belly. Pull the tailbone down to the floor slightly and the pubis toward the navel. With a steady breathing, keep the shoulders relaxed and opened, look straight ahead at a fixed point in front of you and concentrate on the breathing.
This posture helps to promote confidence and happiness, it also improves posture and creates space within the body, allowing the internal organs to work more efficiently thus improving respiration, digestion and elimination.
Tadasana is the basis for many standing postures. Urdhva Hastasana is a very similar posture with the hands raised above the head.
The Mountain pose helps to tone and strengthen the abdomen and the legs. It may help to relive back pain and reduce flat feet. Postures that help prepare for Tadasana include Adho Mukha Svanasana and Uttanasana.