This is Fitbit's application that allows you to upload your Tracker's stats from your base station to your personalized dashboard on Fitbit.com, so you can track your activity, log food, and much more.
The base station will wirelessly syncs data from your Tracker to your computer, whenever you are within about 15 feet. You'll also use it to charge the Tracker's battery every 5-7 days.
Moreover, during the software installation, you'll link your Tracker device to your Fitbit.com account by placing it on the base station and entering a code.
Leave your Tracker on the base station until the battery is fully charged (press the button while on the base station to see the battery indicator).