USB Bluetooth dongles are plugged into the USB port of a computer. Along with being plugged in, the user must subsequently install the drivers and software packaged with the dongle on the computer.
Most modern USB Bluetooth dongles are as simple as plugging in, installing software and being ready to use. Most dongles will offer a user interface that allows the computer to connect with available Bluetooth devices.
The purpose of the dongle is to give Bluetooth support to a computer that may not have it. A Bluetooth dongle makes any computer with a USB port capable of using Bluetooth accessories.