What do the terms hypertonic, hypotonic, and isotonic mean?

Hypertonic is more concentrated, Hypotonic is less concentrated and Isotonic is equal.

A Hypertonic solution is a solution with a higher concentration of salts than the cell, or a has a lower water potential. In this case, water would be lost from the cell to the solution my .

A Hypotonic solution is the opposite ie, a low concentration of salts and thus a high water potential, therefore water would be lost from the solution to the cells and the cells would expand.

An Isotonic solution is that which has equal salt concentrations. There is still an exchange of water, however this is at equilibrium so the overall change is zero.