Hypotonic solution means that solution has lower osmolarity (total concentration of all solutes) than the fluid inside the cell. So the fluid (water) will move into the cell.
Hypertonic solution is solution with higher osmolarity then the interior of the cell, so the water will move from the cell out.
Isotonic solution is solution that has the same osmolarity as the cell. This is homeostatic state.
If placed in a hypotonic solution, a cell might explode, while in a hypertonic solution, it will shrivel.
