(n.) A small device or circuit that regulates the voltage fed to the microprocessor. The power supply of most PCs generates power at 5 volts but most microprocessors require a voltage below 3.5 volts. The voltage regulator's job is to reduce the 5 volt signal to the lower voltage required by the microprocessor. Typically, voltage regulators are surrounded by heat sinks because they generate significant heat.
Some voltage regulators, particularly those packaged as a voltage regulator module (VRM), are voltage ID (VID) programmable, which means that the microprocessor can program the voltage regulator to provide the correct voltage during power-up.