Question:   I don't understand osmosis.  If you have two solutions separated by a semi-permeable membrane, what direction will solvent move to?

Answer:

Osmosis is when solvent molecules move across a semi-permeable membrane from a less concentrated to a more concentrated solution.  This occurs in order that both solutions will end up having the same concentration.  For example, osmosis keeps plant cells inflated with water, as pure water is drawn from the trunk of the tree to the relatively concentrated solution within the cell.

When we say that a membrane is "semi-permeable", all we're really saying is that solvent molecules can pass through it and solute molecules can't.  As a result, if you've got sugar molecules (or anything else) dissolved in a solution, these molecules won't pass through the membrane unless it tears.

"Osmotic pressure" is the pressure caused by solvent molecules pushing into a region containing a more concentrated solution.  For example, if the pressure inside a plant cell was 10 kPa higher than the pressure outside the cell, we'd say that the osmotic pressure was 10 kPa.  An interesting use of this phenomenon occurs in reverse osmosis water purification plants.  In these plants, salt water is pushed through a semipermeable membrane hard enough that water molecules pass through but the salt molecules stay behind.  This is exactly the opposite of regular osmosis (as you're pushing solvent molecules from a higher concentration solution to a lower concentration solution), and can only be achieved with very high pressures.