they are still called beam laser/cannon etc. except they have a little turret icon next to the name. The fixed versions show a crosshair, the gimbals show their own hard to describe icon, and the turrets have an icon that looks like a little turret.
EDIT: Found a picture:
View attachment 41083
Gimballed are easier to use than fixed, multicannons are easier to hit with than cannons. Otherwise it's more about personal preference and what works best with your ship.best cannon weapon for newbie combat? best laser for newbie combat?