A pendulum clock is a timekeeping device that uses a swinging pendulum to regulate its movement. The pendulum swings back and forth at a consistent rate, allowing the clock to keep accurate time. This design was first popularized by Christiaan Huygens in the 17th century, marking a significant advancement in horology. The basic components of a pendulum clock include the pendulum, a gear train, and a clock face. The pendulum's length determines its swing period, which is crucial for timekeeping. These clocks are known for their precision and were widely used until the advent of more modern timekeeping technologies.