The multimeter or multi-tester goes by several names but is a compact electronic device, usually hand-held, that measures AC and DC voltage, amperes (current) and ohms (resistance).
The device display may be analog and use a calibrated meter with a needle but is more commonly found in a fully electronic display version. The device has two electrical wire leads, red and black, and a dial to select the setting / mode. Various tests can be run and measurements made depending upon the setting. Electronic versions of the multitester are called a DMM (digital multi-meter) or DVOM (digital volt-ohm-meter).
Voltmeter, Multimeter, Multi-tester, Volt-Ohm-Meter, VOM, Continuity Tester, DMM, DVOM