Lifestyle physical activity is defined as the daily accumulation of at least 30 minutes of self-selected activity which includes  leisure, occupational or household activity that are at least moderates to vigorous in in intensity and are part of everyday life. Lifestyle activity usually involves a mix of walking and other activity such as gardening, doing chores or playing.  Lifestyle physical activity. (2007). Current Treatment Options in Cardiovascular Medicine,  1(3), 203-205.

Many people use walking to get from place to place.  Some recommend that when persons do everyday tasks that are less than 1 mile round trip, that they consider walking instead of mechanical forms of transportation. 

Purposive exercise has been recommended for persons that do not get sufficient activity through other methods or who need specific activity for health.

Exercise can be viewed as a subset of physical activity and often refers to structured physical activities such as sports. Often involving purposive and repetitive movements.

http://www.who.int/dietphysicalactivity/factsheet_recommendations/en/index.html