Entropy:Entropy refers to the measure of disorder or randomness in a system. An example would be an untidy desk with papers scattered everywhere.
Closed System: A closed system is one that does not exchange matter or energy with its surroundings. A sealed jar containing gas could be an example.
Equilibrium: Equilibrium refers to a state where there is no net change in a system. For instance, when temperature inside a room matches the temperature outside, they are said to be in equilibrium.