# What does Entropy mean, other than just “disorder of the system”? Could it be called “Tendency to move towards Thermal Equilibrium”?

What is meant by Entropy? My professor tells me "disorder"(I make no comments on that, except that it really adds no real understanding). The way the concept of entropy kept developing in class, I was forced to conclude that the statement "Entropy of an isolated system always increases" is equivalent to the statement "An isolated system always reaches thermodynamic equilibrium (among its parts, i.e. all parts of the isolated system reach the same temperature)". If that is so, why invent Entropy? Why not just say "Thermal Equilibrium"? Then, I understand that $ΔS=\frac{q_{rev}}{T}$. Meaning, if the reaction is reversible, Entropy change may be interpreted as heat exchanged divided by temperature at which heat flows. Other than this I have no understanding of $S$ or $ΔS$.

So, What is meant by "Entropy"? And why is $ΔS=\frac{q_{rev}}{T}$? And what is up with this thing called "Disorder"?