Distillation is a pretty basic process that lets you separate substances with different boiling points. Basically, you start with a mixture of substances (eg, ethanol and water) and you heat it up to a predetermined temperature based on the ingredients of the mixture and condense the steam. If all has gone according to plan, the condensed steam will be much higher in the element(s) of the mixture you wanted to isolate. A more complex form of distillation is fractional distillation. Distillation is great fun with ethanol and water as you can drink the results! See distillation of homebrew.