Oil is leaking under the car.
Oil leaks generally will become worse over time. Locations where leaks commonly develop are at the valve cover, oil pan or camshaft and crankshaft seals. The source of the oil leak will need to be located, and then the leak repaired. You may want to enlist the help of a mechanic, such as one from YourMechanic, who is trained to locate oil leaks and can repair the leak.