USB
The standard was made to improve plug and play devices. This means that a device can be plugged into a free socket, and simply work. The computer will notice the device. The computer sometimes installs special software to use the device. The device can be removed after it stops being used. This technology is called "hot swapping". "Hot swapping" means it can be plugged and unplugged while the power is on. The computer does not need to be turned off for people to change the devices.