An accelerometer is a device that measures acceleration, which is the rate of change of velocity. It detects changes in motion or orientation by sensing the forces acting on it. Commonly used in smartphones, fitness trackers, and vehicles, accelerometers help in applications like screen rotation, step counting, and stability control. These devices can be found in various forms, including microelectromechanical systems (MEMS) and piezoelectric accelerometers. They work by using mass and spring systems or electrical charges to measure movement. Smartphones, fitness trackers, and vehicles are just a few examples of where accelerometers play a crucial role in enhancing functionality and user experience.