A 12V 5A adaptor is a power supply device that converts alternating current (AC) from a wall outlet to 12 volts direct current (DC) at 5 amperes. This type of adaptor is commonly used to provide power to electronic devices and appliances that require 12V of electrical input. The 5-ampere current rating indicates that the adaptor can supply a maximum current of 5 amperes to the connected device.