A wet sump is what most production engines have; a pan on the bottom of the engine that holds all the oil(the sump is "wet" with oil). A dry sump engine has a small pan and an external oil reservoir and pump. The pan is just there to collect the oil that drains out of the engine so the pump can send it back to the reservoir. This system eliminates windage and allows for a much larger oil capacity than would be practical otherwise. You can also shift weight distribution by moving the res. "Side-oiler" refers to Ford's 427FE blocks that have a unique oil passage running along the side of the block to better oil the main bearings. This has nothing to do with wet or dry sump oiling as a "side oiler" 427 can be set up either way.