While all races in SFB can move in forward or reverse, the Triaxians can "rotate their warp field" in 120 degree incriments (dividing the 360 degrees of a circle into thirds, thus the name Triaxians) and make the #1, #3, or #5 shield facing the "front" of the ship. So, they can move forwards or backwards in any of the three facings. Their weapons (plasma) arcs reflect this ability by being divided up on these three shield arcs.
Here's a Triaxian SSD. The plasma A is an S-torp that has the ability to be configured as a more powerfull, but shorter range torp or weaker, but longer range torp.