Headsets are devices worn on the head commonly to allow you to use both hands while on the phone.
Those that use these devices are usually on the phone for long periods and/or using the phone frequently.
With improved light-weight micro-electronics and battery life wireless headsets are becoming a lot more popular. This reduces the chances of catching a wire on objects and improves portability.
Batteries are charged when the headset is not in use by placing it back in its cradle (usually at the end of the work shift).