MMO 101
Destiny is different from most shooters: it's an MMO that plays like Halo. That means loot drops, stat-grinding, crafting, and all the features you'd expect to find in games like World of Warcraft or Elder Scrolls Online.
All of that stuff you're picking up off the ground is loot
Loot is a wonderful thing. In Destiny, items drop in the form of white, glowing polygons called Engrams which you can pick up and immediately equip. However, the colored (green and blue) Engrams are encrypted and you'll need to bring them to the Cryptarch NPC at the tower to "decode" the item before you can use them. There are also items you can earn from gaining faction experience, doing crucible matches, and participating in other activities which I'll mention later.
Gun parts and other materials are for crafting
If you played the Destiny beta, you probably came across different types crafting material without even knowing it. In your inventory, there is the option to disassemble any of the equipment you don't want. For the standard grey items, you just get a few glimmer, but if you disassembled a green or higher rarity item, you probably got weapon parts or other material as well.
Strike instances isolate you (and your party) from other players
If you've never played an MMO, you might be a little confused when people start disappearing in front of your eyes during gameplay. No, they aren't dropping off the face of the internet. Those players are most likely entering an instanced game area or a Strike mission. What is that, you ask? It's basically an area that no one outside that player's party can enter with them. They get that area's enemies and loot all to themselves like you would in any other FPS single player mission.
Join huge battles through public events
The other side of the instance coin is public events--a common MMO feature that you will get a lot of exposure to in Destiny. When players are in the exploration areas of the game world, random stuff can happen. Waves of enemies can start falling from dropships, a single, super-strong enemy will make a break for a valuable resource, or sometimes a massive boss will just plop itself right in the middle of an open field. And guess what? You can go and kill those things. But you won't be alone. Any player in the vicinity can join in on the action, and holy shit is it a blast!
Raids are end-game grindfests
In an MMO, the end of a the story isn't the end of the adventure. When you reach the end-game, an MMO usually provides several ways for you to grind for better gear. And one of the most popular activities is running raids. A raid involves gathering a bunch of friends , taking on an incredibly difficult mission, and fighting a huge boss for random, super rare loot drops.
Create a separate armor and weapon loadout for PvP
The Crucible may seem just like a multiplayer match from Halo. You just pick out your favorite gun, get in there, and start cappin' fools, right? Wrong. If you're not equipped with the proper gear equipped, you are going to be at a major disadvantage. Some Crucible modes level the playing field by canceling out all of the armor and weapons bonuses for damage and protection, but you can still use the armor bonuses to your strength and discipline to boost your grenade and ability usage.
Stand out from the crowd by grinding reputation points
Besides repeating raids, playing through story quests, and competing in multiplayer matches to earn equipment, there are other activities you can sink into a bunch of times for special rewards. Factions can provide you with powerful, aesthetically unique items. All you have to do is dedicate some time to your prefered group by doing quests or whatever else they require.
