You either have burned rings and inserts or burned valves now that if you. are burning a lot of oil however if your just losing oil it could be a number of problems but the main cause is a loose valve cover or. VCR gasket
You could have a leak, which continuously drains the oil until the oil light comes on. Another reason is that the engine has a very heavy amount of wear and tear. A normal engine is designed to let a very small amount of oil pass through the pistons. This oil is supposed to leave the chambers through the valve system. I would take your car to a mechanic to have the problem fixed.