Wrong:
I explained all this to a gaming acquaintance
Yeah you can do a

ton in the game (Beta speaking, retail will be way bigger)
There's marks for 2 main factions, 1 PVE oriented, 1 PVP oriented
PvE mark is given with Strikes (think dungeons), PTE Public Time Events (think Fates, but happen randomly in a zone, get Gold Rating everyday (think dailies) get +3 marks), trade in material in batches to the Quartermaster of said faction to earn extra marks (need 40 per batch, these are also used to upgrade weapons/gear, so choose wisely)
PvP is your FPS standard modes with twists, Control = Domination + TDM, yes you try to control 2/3 flags, then have to kill opponents, more flags you have the better bonus points you achieve
The players gears are equalized, so if your wearing Rare (Blue) items and fighting Uncommon (Green) Opponents, you will not have an advantage, the damage/impact is the same for all weapon (think level capped), your gear/weapon leveled attributes do carry over
There's also events that Bungie will throw in from time to time for rare factions that only appear during it, the same game modes you play now will have the advantage gear enabled, so now people with Uber gear will stand out against lower geared players (It's called Iron Banner), mostly matchmaking will try to match players equally geared towards a rating, or people will get annihilated by better geared players
There's a 100 mark cap every week, so a win gets you +2 a loss +1, so you can't grind PvP
Then there are sub factions that give good loot if you earn reputation on their behalf, which in turn you level up their reputation rank and earn marks to buy their emblem gear
The farming parts comes from Strikes and Explore (just going back to story missions w/o being zone in, can go explore all areas, kill mobs for ammo/xp/engrams (think sacred scrolls that need to be deciphered)
Cryptarch takes those engrams and deciphers them, thje more you decipher, the more he levels up, the more he levels up, the better rarity those engrams become
A Cryptarch with Rank 5 might decipher a Rare (Blue Engram) into just materials that are rare, but a Rank 10 might hand you a Blue Gun
Currency in this game is called Glimmer, you get them from chests (people do loops and farm them in a zone) or higher rank mobs that drop them, rewarded also, and gear/weapons you don't need/use can Dismantle and make small amounts of glimmer but also net you materials
Yes the game has synthing process for gear and weapon upgrades, you need certain materials to open the skill tree and upgrade talents within gears and weapons
You cap out at level 20, but you can keep overleveling (think ilvl) with the Light stat
Certain gears (Legendary (Purple) and Exotic (Gold) have Light stats on them
You need those to do higher level dungeons where mobs get to level 31, so more +Light the better you will be against those. I theorized that for every +13 Light, you gain a level
The last thing is when you are geared the

out and almost maxed out, you go do Raiding (think Coil)
So far one in announced called Vault of Glass, this must have the best gear possible
Also you can only win loot once, you can repeat the raid (not fully guaranteed), but loot is once a week till reset
There's also a checkpoint system, so you can come back and pick up from where you previously left off
So yeah this game is crazy for trying to merge many genres and use the FPS model as the overlay
Rarity gear:
Common (White) < Uncommon (Green) < Rare (Blue) < Legendary (Purple) < Exotic (Gold)
You can only equip an exotic on each side of you char, for a total of 2
Left side pick either, primary, secondary, heavy
Right side pick Head, Chest, Legs, Feet
You can't exotic out your char, take a look here at this video:
https://www.youtube.com/watch?v=aR42-WbyamA, you'll see the exotics and how some are ridiculous good looking
3 classes Titan, Warlock, Hunter, there's no defined roles that there has to be a tank or healer
All 3 are up to the job, each do differentiate themselves within their skills/talents
Once you hit 15, you can choose a subclass, each class has 2 subclasses at the moment
1 offense, 1 defense, you can level those up and swap them in out for the situation at hand
I'm still missing stuff here, but this is the gist of Destiny
It's a time-sink, but nothing like XIV requires