Voltage testers can have slightly varying purposes; their capacity to test voltage means they can also detect it and subsequently perform a continuity test. Voltage testers are used to identify whether electrical items are functioning safely at the levels they should be.
Voltage testers are used primarily on AC currents, although some can also be used on DC currents.
Voltage testers are used to detect live electricity and tell you the voltage level, however they need to come into contact with the supply.Voltage testers can be used on sockets and other access points, like fuse boxes.
Most electrical items have a set voltage at which they should be running. It may be beneficial to know the voltage levels to see if things are working as they should. For example, if batteries are running at a lower voltage than stated, they may need recharging or replacing. This is also why a voltage tester may be preferred to a voltage detector, as the voltage detector cannot give you a reading.