A pendulum is a weight suspended from a fixed point that swings back and forth under the influence of gravity. It consists of a mass, called a bob, attached to a string or rod. When the bob is pulled to one side and released, it moves in a regular, repeating motion, known as oscillation. The time it takes to complete one full swing is called the period, which depends on the length of the string and the acceleration due to gravity. Pendulums have been used in various applications, including clocks, where they help keep accurate time. The famous Foucault pendulum demonstrates the rotation of the Earth by showing the change in the swing direction over time. Pendulums also play a role in physics experiments and can illustrate concepts like energy conservation and harmonic motion.