The purpose of the alternator regulator is to convert the AC current supplied by the alternator into a DC current, and to feed it into your electrical system at the correct voltage. It also ensures that all the vehicle's electrically powered equipment receive enough power for the function they perform. However, the regulator, as part of the alternator, may fail, in which case your vehicle's battery will no longer be charged, or will even be overcharged. If this happens, it's high time for a new regulator.
The regulators available to buy are the same as the original in their design and performance.