Kung Fu (功夫) is the ability obtained from hard work and can be used in many contexts. Wushu (武術) is a term that defines any type of martial arts activiy.
The term Wushu is also the name of a modern sport, similar to gymnastics, involving the adaptation of forms and sequences of bare hands or chinese weapons where the competitor is judged and given points according to specific rules.
Yau-Man Kung fu characteristics:
Stable inferior members (馬步 - mabu);
Quick and precise movements;
Firm and agile steps
Agility and dexterity on superior members and torso;
Defense reflex and counter attack
In addition to the skills achieved by training, Kung Fu also provides the benefit of health preservation, supporting psychic and physical balance