Aerobic activity is focused on increasing your heart rate a moderate amount and keeping it increased for a moderate period of time. 

Aerobic activity includes walking, jogging, running, swimming, rebounding (on a mini-trampoline), dancing, skipping, jumping rope, cross-country skiing, skating and probably several other kinds of activity.   If I left off your favorite aerobic activity, click here to email me.  

Of all the aerobic activities, walking is often considered the best because it is easy on your joints. 

Swimming is often listed as second best.  It is easy on joints but it isn’t a weight bearing activity so it doesn’t build bone as much as walking.  For the same reason (buoyancy reduces weight) swimming is considered the best activity for those who are very heavy (obese) because it eases the stress on your joints while you exercise.

Which is the best aerobic activity for you?  The one you enjoy the most.  That is the one you will be motivated to stick with.