What is Wing Chun Kung Fu

Wing Chun is a very scientific close range combat system. Because it was developed by a woman, its sole purpose is to use the least amount of time and physical strength to defeat an attacker of bigger size, so its movements are non-flashy and straight to the point. Unlike other martial arts that involve a lot of jumping, high kicks, big swing and wide movements with brute strength, Wing Chun emphasizes the principles of Economy of motion, Economy of strength and Sensitivity.
Economy of Motion
The shortest path between you and your opponent is a straight line. Based on this principle, Wing Chun uses the most direct and simplest movement, along the shortest path to attack the opponent. Economy of Motion also emphasizes the use of simultaneous attack and defense. Rather than executing attack and defense in two different motions, Wing Chun always strives to execute both in the same movement.
Economy of Strength
Economy of strength studies the most economic use of body mechanics and structure to neutralize the opponent's force and to generate its soft yet explosive power. Scientifically, impact power of a punch comes from Mass and Speed. Assuming the mass (the size of your fist) stays the same (although Wing Chun uses different exercise to condition our fist or knuckles), the power of your strike mainly comes from speed. In Wing Chun, the maximum power comes in 3 steps. Giving up your strength, meaning not tightening your arm muscle in forearm, bicep and shoulder, will increase speed, thereby power. The second step is the deflection of strength. Rather than using strength against strength, Wing Chun uses skillful deflection to dissolve opponent's power. Then the third step is to borrow strength. As long as the opponent's power is deflected just enough so that it doesn't directly impact our body, then we can use his strength so that opponent will run into our strength.
Sensitivity
Wing Chun is very realistic. It realizes that our opponent isn't just standing there for us to hit. He will move and he will block. Also each opponent's reaction will be different, they won't necessarily react the way as we like them to react. There is definitely no time to stop and think about how do deal with certain reaction. For any untrained fighter, upon contact, most people will naturally resort to using strength to fend off the opponent. However, Wing Chun places very heavy emphasis on the feeling of the opponent’s energy and direction upon contact rather than relying strictly on sight. When a contact is made (whether you are attacking or blocking), the most economic movement will be executed right at that instant. Through many sensitivity exercises, these economic movements will come naturally as a reflex.