What is a lipid and what functions does it serve?

Lipid - any of a class of organic compounds that are fatty acids or their derivatives and are insoluble in water but soluble in organic solvents. They include many natural oils, waxes, and steroids.

Its plays the role of storing energy or forming cell membranes alone.

Lipids are fats and they are used in the body for providing energy and storage. it can also be used for other things like helping with hormones, protection for your body (it is fat after all) and helping with the cell wall structure. hope this helps :-)

Yes yes yes very good