Explain the Factors that Affect a Reversible Process

This is a Thermodynamics Essay in the Field of Mechanical Engineering. It is essentially about discussing what a REVERSIBLE Work/Energy Thermodynamic Process is (briefly) and what are the factors that affect it, such as Friction, Unrestrained Expansion, Heat Transfer, Mixing, etc. (mainly)

A reversible process is basically the one that having taken place, can be reversed in a manner that it leaves no change in the entire system or surroundings; thus, it is the process that supplies maximum thermal efficiency. A writer familiar with Thermodynamics concepts is preferred.