think of the small chain ring on the front as regular gears. going around town, regular riding kind of stuff. depending on your gear ratio and your ability - most of your riding will be done here.

think of the large chain ring on the front as your overdrive. this is useful for when your spinning too fast in the small chain ring. you'll need to use it much less i'm sure. i rarely use my large chain ring (only use it for speeds above 24mph).