Simple distillation is a process used to separate two or more liquids with different boiling points. It involves heating a mixture of liquids in a distillation flask, and the liquid with the lower boiling point vaporizes first. The vapor rises through a condenser, where it cools and condenses back into a liquid. This liquid, known as the distillate, is collected in a separate container. The remaining liquid in the flask, which has a higher boiling point, is called the residue. Simple distillation is commonly used in laboratories and industries to purify liquids or separate components from a mixture.