Disitllation is the separation of liquids based on their separate boiling temperatures. 

For our purposes, this relates to the fact that ethanol boils at 78C or so, and water not until 100C. So in theory, heating a solution of alcohol and water to 80C would mean the alcohol would evaporate and the water would stay behind. If we collect the steam that is evaporating, and cool it down, it will return to liquid form and we’d have separated the alcohol from the water.

in practise, this is messy. The two liquids when combined share a boiling point which makes the process highly inefficient, which is in fact a good thing as it allows for a myriad of results and the plethora of spirits available to us.

It’s pretty hard to beat this definition in the button below