Where do most petroleum products come from?

From oil that is found beneath the surface of the Earth.

When pumped out of the ground, it is referred to as crude oil.

It is typically processed by a company/ies to make the products that you consider "petroleum products (e.g.: fuel (gasoline/petrol/jet), lubricating oil (motor, gear, bearing), heating (#1-#6, kerosene, residual oils, etc).