The EcoMotors engine is an "opposed piston" engine. There are two pistons in each combustion chamber: http://www.ecomotors.com/videos/introduction-opoc-powertrain
Porsche and Subarus are "flat" or "boxer" engines. Much more conventional, where instead of a V angle they are laid flat (basically a 180° V). There are some distinctions in calling an engine either flat, boxer, or 180° V: http://en.wikipedia.org/wiki/Flat_engine
As Rob mentioned, the pistons in each cylinder work off of each other, using parts of the combustion cycle that would typically be waste to create another power stroke. Pretty neat looking if they can make it reliable!