When you set up your device, you specify your baseline activity level. So it doesn't inherently know that the activity you're getting at work, for example, is part of your everyday routine. If you set it to active, it will assume you burn more calories throughout the day than someone who is more sedentary. It will still track your exercise the same way- as long as you're getting 10 minutes of continuous movement it will track that as an exercise "event". (Most people with active jobs likely do a lot of stopping and starting, so that movement wouldn't mistakenly be recorded as exercise.)
Hope that helps,
"You may have a fresh start any moment you choose, for this thing that we call "failure" is not the falling down but the staying down." Mary Pickford
"No matter how slow you go, you are still lapping everybody on the couch."