When your oil light is coming on it's usually caused by a low oil pressure condition in your engine.
It could mean that your oil needs changed and your oil filter could be clogged which is not allowing enough oil pressure to flow through your oil pump and through your engine.
Your engine needs the proper amount of oil pressure so that the oil gets pumped through the engine and lubricates the valves, valve springs, engine bearings, pistons etc.
When the oil pressure is low then the engine doesn't get lubricated properly which can then lead to engine failure so get the oil pressure checked out.
Your oil could also need changed or you might need a new oil pump but usually the oil pump lasts the life of the vehicle.
The oil pump is inside the oil pan on most vehicles so you have to remove the oil pan to get the oil pump off the engine.
The oil pressure when at idle speed should be between 15 PSI to 20 PSI and when the engine is at higher RPM the oil pressure should be between 45 PSI and 55 PSI but can sometimes go as high as 60 PSI which is normal.