From NuGOwiki

The term lipid comprises a diverse range of molecules including waxes, fatty acids, fatty-acid derived phospholipids, sphingolipids, glycolipids and terpenoids. Lipids are a class of hydrocarbon-containing organic compounds and categorized by the fact that they are soluble in nonpolar solvents (such as ether and chloroform) and are relatively insoluble in water. Lipid molecules have these properties because they consist largely of long hydrocarbon tails which are hydrophobic in nature. In living organisms, lipids are used for energy storage, serve as structural components of cell membranes, and are important hormones or contain essential fatty acids. Although the term lipid is often used as a synonym for fat, the latter is in fact a subgroup of lipids called triglycerides. Find more on information on lipids on Wikipedia.