The Time-of-Flight principle (ToF) is a method for measuring the distance between a sensor and an object, based on the time difference between the emission of a signal and its return to the sensor, after being reflected by an object.
Time of flight sensors measure the time it takes something to travel a distance through a medium. Typically, this is the measurement of the time elapsed between the emission of a wave pulse, its reflection off of an object, and its return to the ToF sensor. A time of flight camera is a device that utilizes ToF measurement to determine distances between the camera and objects or environments, creating images generated by individually-measured points.