A boxer engine is also sometimes referred to as a flat engine. For a spot of context, most cars use inline or V-type engines. These engines are tall and narrow, as the pistons are configured and move vertically. However, a boxer engine is designed so that the pistons are firing and reciprocating horizontally. It's called a boxer because of how the pistons fire towards each other from both sides of the crankshaft, as though two boxers are throwing punches at each other. This allows a boxer engine to sit flat and low to the ground, further lowering its center of gravity. Another upside to boxer engines is that they're naturally smoother and more fuel-efficient compared to a typical inline or V-type engine. Few brands use boxer or flat engines, besides marques such as Subaru or Porsche.