Pushing hands is a two person exercise to further develop the skills learnt by the practice of Form that is learnt is a safe and gentle way, with two people working together to improve their skills, emphasizing softness and relaxation.
The first skills that learnt are those related to "listening" energy (Ting Jing), where the partners are developing sensitivity in their hands and learning to "hear" what their partners are going to do.
They then go on to develop "neutralizing" energy (Hua Jing), where the incoming energy is diverted or returned to the partner. This is where the skills related to the often quoted maxim of "using 4 ounces to deflect 1000 pounds" are honed.
From here the skills of "discharging" energy (Fa Jing) are developed, enabling the exponent to apply energy whether pushing, punching or kicking.
Once these basic skills are learnt, the practitioner learns to move about and develop their skills at freestyle pushing hands and can practice all the skills they have learnt while moving around.
"An army without flexibility never
wins a battle.
A tree that is unbending is
-Dao De Jing