When water and sugar are mixed together, they become a solution. A "solution" refers to any two substances that become a single phase when mixed together. Because the sugar dissolves into the water, it is known as the solute. The water, which does the dissolving, is the solvent. You can use the basic process of evaporation to remove sugar from water.
Pour the sugar water into a pot.
Set the pot on the stove, and turn the stove to medium heat.
Let the water boil. As it boils the water will evaporate.
Check the boiling process regularly. As the water boils, sugar crystals will form along the sides of the cooking pot. Once all the water has evaporated, remove the pot from the stove and you'll be left with just the sugar remaining in the pot.
Check the boiling process regularly. If you leave the sugar in the pan after the water has evaporated, the sugar will be burnt.