This shows a list of nearby or paired Bluetooth devices. The list will include "visible" Bluetooth devices that are nearby, that you may wish to pair with, or it may include devices that are already paired that you may wish to do something with.
Pairing with a new device
If you wish to pair with a new device that is not already paired, tap its name in this list, and a pair request will be sent to that device. For security reasons, the device needs to confirm that you wished to pair it before responding: if the device has a screen, it may pop up a message asking if you want to confirm, but if the device is a simple device like a wireless headset, keyboard or mouse, it may just display a flashing light and require you to push a button to respond.
Once you have confirmed the pair request on the other device, that device will respond to the first device and they will be paired. Once paired, the two devices will connect whenever they are in range of each other and switched on (and Bluetooth is switched on).