Whr did ALL of my engine oil leak out onto the.

That's all the detail you can provide? You'll have to hold your computer closer to the car so we can see it. How fast is it leaking? Is there any left in the engine at all? Did this happen while it was parked with the engine not running or does it only happen with the engine running? Have you actually looked for the source? How high up do you see oil on the engine? Which side, front, or rear? Was the oil just changed and the gasket from the filter stuck to the engine? Was the fill cap left off and oil sprayed out? What size engine do you have?