Light activity includes any form of movement, such as walking slowly or even just moving around the house.

Moderate activity, such as riding a bicycle, fast walking or playing badminton, will raise your heart rate and make you breathe faster and feel warmer. 

Vigorous intensity activity, such as running, playing tennis or football, will make you breathe hard and fast. This is great for a good cardio workout but you should be fairly fit in order to exercise at this level.