This document summarizes key information about lipids. It defines lipids as water-insoluble biomolecules that are highly soluble in organic solvents. Lipids are classified by their origin as fats, oils, or plant and animal lipids, and by their consistency. The structure of lipids is also outlined, focusing on triacylglycerols and fatty acids. The roles of lipids in the human diet and in the body are described, including as fuel, energy storage, signaling molecules, and as structural components of cell membranes. Finally, the main lipids that make up biological membranes - phospholipids, glykolipids, and cholesterol - are introduced along with some aspects of their structures.