Phospholipids are molecules made up of a phosphate head and fatty acid tails. Phospholipids are hypdrophobic molecules meaning they are water insoluble. They are important because they make up the membrane of the cell. The phospholipids are arranged in double layer called a bilayer with the phosphate heads facing outward and the fatty acid tails facing inward. The cell membrane is necessary to separate the inside contents of the cell from the external environment. Some phospholipids called lecithins are used in foods we eat.
Source: concepts in Biology. 12th edition. Copywright 2007 McGraw-Hill