Laser-cooling techniques are methods used to reduce the temperature of atoms or molecules by using laser light. When a laser beam is directed at a gas of atoms, it can slow down their motion by imparting momentum to them. This process lowers the thermal energy of the atoms, effectively cooling them to near absolute zero. One common technique is called Doppler cooling, which takes advantage of the Doppler effect. By tuning the laser frequency slightly below the atomic absorption frequency, only atoms moving towards the laser light absorb photons and lose energy, leading to a decrease in their overall temperature.