Mac OS X Leopard/Part 3/System Preferences/Bluetooth
This pane contain settings that affect Bluetooth on your Mac. This pane is only enabled if you have a Bluetooth receiver either internally or externally. You have two checkboxes at the top as seen in the picture. On will turn on Bluetooth. If you don't need Bluetooth, you can safety turn off this box. Discoverable will make the mac "advertise" the bluetooth signal from the computer. You should normally turn this off if you are not connecting any devices for security reasons, and it is not needed after you connect a device.