A voltmeter is an instrument used to measure the electrical potential difference, or voltage, between two points in an electrical circuit. It is typically connected in parallel with the component or section of the circuit being tested. Voltmeters can be analog, using a needle and scale, or digital, displaying readings on a screen. These devices are essential for diagnosing electrical issues and ensuring that circuits operate within safe voltage levels. They are commonly used in various fields, including electronics, engineering, and automotive repair, to monitor and troubleshoot systems effectively.