[Sticky] Weapon Types, Classes, Perks, and Elemental Damage
One great thing about Destiny 2 is the volume and variety of weapons in the game. This can also make things a little confusing so I have tried to collect as much information from around the web from sources that have done a lot of research into this.
First things first, there are three classes of weapons: Kinetic, Energy, and Power. This works out great because you get three class-assigned weapon slots, so you will always have equipped one of each type.
Kinetic weapons are your standard weapon of choice and behave like a typical gun you would encounter in any other shooter. The primary role of the kinetic weapon is to do damage to un-shielded enemies health bars and do so more effectively than energy weapons.
Energy weapons shoot pew pew lasers and stuff which come in three elemental flavors...arc (lightning), void (magic?), or solar (fire). Energy weapons are used for bringing down enemies shields quickly. It is important to know what element of shield you will be encountering because destroying a shield with an energy weapon of the same type will result in an explosion which if your character is cool enough, will walk away from without looking.
Reddit user u/Kitsunekinder did all of the testing comparing kinetic v. energy in all situations and it is a good post to check out.
Power weapons are your heavy-hitters, and due to the limited ammo capacity are going to be used in specific situations such as boss fights or to eliminate a large pack of mobs quickly.
Within these classes, there are various types of weapons. There is some cross-over but not every type of weapon shows up in each class (for example there is no Kinetic Rocket Launcher).
Auto Rifles - these are a fully automatic weapon class, sporting a fast fire rate to deliver consistent damage. However, this often results in strong recoil, which can be hard to control over distances. This class of weapon is usually best suited for close range as a result, with some weapons stretching to medium ranges..
Sidearms - these provide a high rate of fire, but struggle with both range and stopping power. While they can be a valid tool against close enemies, sidearms traditionally struggle to deliver steady damage in most situations.
Scout Rifles - packing high impact and accuracy, and frequently excelling and medium to long range. Due to the low semi-automatic fire rate, recoil is rarely an issue with this class of firearm with the ability to fire long-distance shots with the assistance of a zoomed scope.
Submachine Guns - the SMG delivers unrivaled fire rates for a fully automatic weapon. With less stopping power per round, these firearms often have more controllable recoil, too, although range suffers. As a result, SMGs should be used strictly in close quarters situations.
Hand Cannons - short to mid-range attack delivering heavy damage in exchange for a shorter range. However, these weapons are unrivaled for precision at close range, sometimes offering easy headshot kills against mobs.
Swords - swords deliver a deadly strike in close-quarters and can be devastating in crowds.
Shotguns - delivers a heavy, forceful blow at close range, firing multiple projectiles in a spread. The traits of shotguns can vary but commonly provide high damage, with a relatively low number of shots between reloads.
Pulse Rifles - these deliver damage in set bursts, usually three rounds per trigger pull. Although a burst can maintain better stability than over longer ranges, they fail to deliver the accuracy of Scout Rifles. While an adaptable rifle, these weapons are best used at medium ranges
Sniper Rifles - deadly marksman weapon designed to eliminate enemies in long-distance engagements providing access to high-zoom scopes and unmatched stability.
Rocket Launchers - a devastating weapon that deals heavy explosive damage through a slow-moving projectile. Upon impact, shots fired from this weapon deliver damage across a wide radius.
Grenade Launchers - fires a grenade that detonates with the pull of a trigger. It is very effective in wiping out close groups of enemies.
Fusion Rifles - these short to mid-range weapons must be charged up before firing, and they deliver damage in a cluster of concentrated energy bursts. The traits of these rifles can vary from model to model, but they generally deliver heavy damage and a sizeable charge-up period.
Weapon (and armor) Mods are a way to customize and power-up your items. For a complete and in-depth list of available Mods please check out this great resource.
Weapon Perks are additional characteristics that make a weapon unique, and sometimes extremely powerful in certain situations. Weapon perks are fixed on weapons, but most high-level weapons will have a few perks you can choose from. There are literally hundreds of perks so depending on the situation you encounter you may be looking for a weapon with a specific perk. Luckily, someone has done all of the work for you figuring out which perks exist on which weapons. Not only does this page have all of the perks it will search for weapons that contain the perks you filter for.