An accelerometer is a small device that measures acceleration, which is the rate of change of velocity. It detects how fast something is moving and in which direction. Commonly found in smartphones, fitness trackers, and vehicles, accelerometers help track movement and orientation. For example, they enable features like screen rotation in smartphones and help fitness trackers monitor physical activity. These devices work by using tiny sensors that respond to changes in motion. When the device moves, the sensors detect the force of acceleration and convert it into electrical signals. This information can be used in various applications, from gaming to automotive safety systems.