can you explain the concept of liquefaction of gases, and the various methods of acheiving it ?

Gases have a lot of intermolecular distances. By reducing the temperature the K.E reduses, if the temperature reduced below the critical temperature of a particular gas it changes to liquid. If the Pressure alone is increased the gas compresses the vanderwaal forces act and gas liquifies above the critical pressure.

Compression brings the molecules in close vicinity and cooling slows down the moment of molecules therefore , intermolecular interactions hold the closely and slowly moving molecules together and the gas liquifies.