Multi meters are designed to safely check  the circuit for power. They are used primarily to test circuits for problems. They can measure voltage, amperage, micro faruds, milli amps, ohms, and capacatance.

They are two major catagories; a digital meter and a analog meter. The digital meter is one of the most common types because it is the simpliest to use. When set to, for example voltage, it will automaticaly determine the range setting. An antalog meter will need to be manually set for the proper range. Without the proper range, the voltage reading will not be accurate. Using the analog meter requires more experience and knowlege than using the digital meter.