In martial arts we know that having a strong and grounded stance is extremely vital during a fight, especially in combat against a grappler; Jiujitsu, Judo, Aikido styles for example.
Losing balance in a serious life-threatening situation also means you have likely decided the outcome of the confrontation.
There are many different ways to improve the coordination of the body in order to control the falling, but physical training that does not teach the student to draw the natural Qi energy from the earth will not help him much against a powerful push.
Rooting Technique (of Taiji) is a method of developing the capacity of internal energy Yin and Yang sufficient enough to connect with the Earth Yin qi (gravity). It does not mean to holding a low stance and train to having strong legs, it means to calm the mind and understand the way how the body can stay in harmony flow with the universe.
One who is able to tap into this energy, his body becomes fully aware and at peace. The stance will be as strong as a big tree with its roots dwell deep under the ground. In reality, the rooting technique does not counter an incoming force, it listens then redirects or dissipates all the power of that force to the ground. Or if intended, the practitioner can reflect it back to the attacker.
The following video clip is an excellent demonstration of the 70 year-old Master Chen Xiaowang on Taiji Rooting Technique. On the second video, he was in a friendly 3-round one minute match against one of the Asia strongest men.
Here is another video of master Chen Zhenglei demonstrating Taichi Rooting.
Master Yip Man (Wingchun style : Gee Kim Yeung Ma Stance) also demonstrated this technique many times to his students and even in one of the fight against the bullies in the restaurant to save his friends.