How a laser can measure the distance?

To put it simply, a laser distance measuring device consists of 2 basic parts; an (laser) emitter and a receiver. The emitter part knows when it is transmitting pulses of laser light and is synchronized with the receiver. The laser light beam is travelling at the speed of light, so the distance travelled is calculated based on the AMOUNT TIME IT TAKES TO REACH THE RECEIVER, that its round trip time divided by 2.