Most people think of lipids negatively because they associate them with fats. Although some lipids are classified as fats, lipids are not "bad." On the contrary, they provide very important functions in the body.
Lipids are diverse compounds that are grouped together because they are insoluble in water, but soluble in nonpolar solvents such as ether. Common lipid types include fats, phospholipids, and steroids. These lipids have various functions in the body.
Fats are composed of fatty acids and glycerol. They store energy, help to insulate the body, and cushion and protect organs. Phospholipids contain two fatty acids and are a major component of cell membranes. Steroids are cholesterol derived hormones that regulate various physiological functions in the body.