Closed loop system

A Closed-loop Control System, also known as a feedback control system is a control system which uses the concept of an open loop system as its forward path but has one or more feedback loops or paths between its output and its input.

In these systems, the output signal is compared to the input signal to correct errors and adjust the control action to the value required.

Two very common examples of closed loop systems people use frequently are temperature control systems (house thermostat) and cruise control systems (in vehicles). 

Both rely on feedback and a closed-loop system to make automatic adjustments without input from a user, other than creating a set point.