The experiment ATLAS (A Toroidal LHC AparatuS) will start in few months its operation. ATLAS consists of many subsystems. One of the subsystem is the Muon Spectrometer. A detector that is a part of Muon Spectrometer is the MDTs (Monitored Drift Tubes). In my talk, I will try to present the very basic physical concepts behind the operation of MDTs and the Experimetal Setup that is needed for the comissioning of MDTs before and during the operation of ATLAS detector.