Fixed - Always pointing forward and going to be in the middle of your screen. These have no damage penalty, however you have to aim by moving your ship. For thermal weapons (no projectile), this is extremely easy to use fixed as long as your ship pitches, yaws, and rolls fast enough. However with kinetic weapons, you have to lead the shots. There's a reticle that helps you lead them, but there is a challenge there. Some weapons only come in fixed, off the top of my head two of which are Railguns and Plasma Accelerators. They're both very strong weapons and would probably be pretty OP if they came gimballed or turreted.
Gimballed - Can aim in front of you whether your ship is pointing right at the enemy or not. It will automatically lead the shots for Kinetic weapons.There is a damage penalty for gimballed weapons though, however this can often be worth it since actually hitting the enemy is better than not hitting them. Most recommend gimballed weapons on ships that can't pitch, yaw, and roll incredibly fast and on kinetic weapons. There's also another drawback to gimballs: Chaff and Silent Running screw them up. They track heat, chaff makes them go all over the place, and the enemy going into Silent Running makes you lose targeting of them.
Turreted - Can aim almost full 360, but this is very dependent on the position of the hardpoints on your ship. There's a damage penalty with turreted weapons too, but again, like the gimbals, in some cases hitting things for less damage is better than not hitting things. Turrets will keep firing when you lock onto an enemy, whether you can actually see them right in front of you or not. It can be very useful if you can't turn quickly enough to be able to aim at them normally. Like gimballs, they can also get screwed up by silent running and chaff. I'd recommend turreted weapons for the larger ships that can't pitch, yaw, and roll very quickly. I use them on my Anaconda (part of the trifecta of largest ships in the game), many others do too.
Which one you need really depends on your ship's capabilities and the situations you'll often face. as an example, here's a few loadouts I have had in the past (and some in the present):
Vulture (Haven't used it in a while, but I think I still have this same loadout) - Large Fixed Beam Laser, Large Fixed Pulse laser. I never have to worry about running out of ammo, the Vulture is extremely agile, so aiming a fixed weapon is not an issue at all.
Fer-De-Lance (old) - Huge Fixed Plasma Accelerator (PA's only come in fixed), 4 gimballed Medium pulse lasers
Fer-De-Lance (current) - Huge Fixed Beam Laser, 4 gimballed multicannons
Anaconda - 3 Large Turreted pulse lasers, one Huge Cannon, two medium railguns (only come in fixed), two small railguns (only come in fixed).
Especially with the Anaconda, I can have the pulse lasers constantly firing at the enemy, and the cannon and railguns I can use when I line up the shot, which doesn't have to be incredibly often.
youregoddamnright.gif
It's interesting seeing stuff like people learning how to dock, or having trouble getting in the mail slot. I do miss the early sense of awe I had when I started over two years ago.