What is an irreversible process and what is a reversible process?

(N/A) reversible process is a process that can be reversed by means of infinitesimal changes in a property of the system without leaving any trace of change on the surroundings. It is an ideal process that occurs in equilibrium at every stage.
An irreversible process is a process that cannot be reversed to its initial state without leaving a permanent change in the surroundings. Most natural processes,such as friction,diffusion,and heat transfer across a finite temperature difference,are irreversible.