Plasma shells are a standard weapon for many units. Plasma Cannons are mostly fairly accurate with the exception of high trajectory plasma artillery. They all deform terrain and have varying area of effect damage. Plasma shells move relatively slowly and are affected by gravity which gives them a balistic trajectory significantly increasing their range downhill while decreasing range uphill. The trajectory also means they can often shoot over friendly units. Their slow projectile speed means most plasma weapons are good against large, slow-moving, or stationary targets, but generally are not as good against fast moving targets or airborne units.
EMG's are fast rapid firing weapons that shoot numerous small plasma bullets. They are effective against any land targets and also against air targets that get in range. They have high damage output but short range. They have a balistic trajectory like the plasma cannon that makes them signifincantly better at fighting downhill. Additionally, bullets from "Heavy EMG"s burst on impact, doing damage in an area of effect.
Laser are accurate weapons that require a direct path between the weapon and target. They have no area of effect with the exception of the Starlight superweapon. Laser thickness is a good indicator of how much damage it does. They have spherical range and thus have their maximum 2D range against units at the same height as them. Lasers instantly hit which makes the constant fire lasers good against fast ground units and air, burst fire lasers can still hit fast units but are not good against them. If the target of a burst laser dies the laser can continue on and deal the remaining damage to units behind the target.
Missiles are projectiles that track their targets. Missiles have yellow exhaust and white smoke. All missiles will attack air, and most missiles will attack ground, except the missiles of dedicated anti-air units (which have blue exhaust). Missile range is not affected by terrain giving them a cylindrical target shape. This is useful as with a large enough height difference missiles will outrange lasers that they would not normally outrange.
Rockets are projectiles that do not track, but continue along their trajectory until impact. Rockets have red exhaust and black smoke. Rocket range, like missile, is not affected by terrain. Some rockets require a direct line to fire which makes them more likely to hit enemies other than their target if they miss. Other rockets have an arcing trajectory that makes them very good at shooting over allies so they can be quite powerful in groups. Rockets are slow so almost never hit air and are poor at hitting fast units.
Heatrays, similar to lasers, require a direct path of fire between the weapon and target. Unlike lasers, the damage falls off with range, so the more distant the target the less damage is done. Close the distance to your target for more damage. Like lasers, they have spherical range.
Fire is a penetrating weapon with cylindrical range. It will do damage to all units in it's firing line. Units hit by fire weapons also catch on fire and will continue to take damage for some time. This is useful for disabling cloak and repair. It can hit fast units and aircraft.
Like fire, gauss is also a penetrating weapon that moves through units. It moves fast, so will only rarely do additional damage to the same unit. It is ballistic like a plasma cannon which increases it's range downhill. The faster projectile makes it able to often hit air and fast units, though it can miss.
Unlike most other weapons, EMP does not directly damage the enemy. Instead it fills up a separate EMP bar on the enemy. The size of a unit's "EMP health" is its current health so damaged units are easier to EMP. When 100% EMP damage is reached (emp damage exceeds current health) a unit is completely disabled and cannot move or return fire. Damage above 100% increases EMP time by 1 second per 2.5% up to a maximum EMP time that is different for each weapon. EMP heals automatically and a unit will be re-enabled once the EMP bar drops below 100% again. Against shields EMP will deal 1/3 of its damage. EMP is yellow, or in the case of the self-destructing tick, blue.
A particular kind of EMP called Disarm will leave the afflicted units able to move, but unable to use any weapons or special abilities. Disarmed units flash yellow instead of blue. Disarm has a separate bar.
Lightning is direct-fire and carries EMP stun along with its damage. It has spherical range. Lightning weapons usually disable their targets before killing them, allowing them to be finished off with no fear of retaliation. Lightning is always blue. Lighting is somewhat inaccurate but should reliably hit any large unit.
Slow damage, similar to EMP, does not reduce enemy hitpoints. Instead it gradually decreases the move speed and rate of fire of enemy units. Like EMP the slow health of a unit is the current health of the unit. The reduction is the slow damage taken divided by the max health of the unit. Slow damage maxes out at 50% and cannot be increased past that point. Like EMP damage, slow damage also automatically heals and deals 1/3 of its damage against shields. Weapons with slow ability are purple.
Many slowing weapons are actually disruptors, represented as purple projectiles or beams with a white core. These do both normal and slow damage.
While this guide covers many of the more common types of weapons, there is still a wide variety of interesting devices at your disposal. The best way to learn them all is to have fun experimenting with them!