definition - What is the difference between implicit, explicit, and total time dependence, e.g. $frac{partial rho}{partial t}$ and $frac{d rho} {dt}$?

What is the difference between implicit, explicit, and total time dependence, e.g. $\frac{\partial \rho}{\partial t}$ and $\frac{d \rho} {dt}$?

I know one is a partial derivative and the other is a total derivative. But physically I cannot distinguish between them. I have a clue that my doubt really might be understanding the difference between implicit, explicit and total time dependence.