Drops are all RNG. Whether they help you or not depends on how you look at them.
1. Equipment to use, pretty self explanatory, but nothing you can plan on.
2. Source of Gold, which means pretty much Vendoring everything you get to a game merchant (as opposed to Guild Stores)
3. Source of Crafting Mats or Inspiration by Deconstructing the items
Outside of Warlock stuff, 99% of what you get during leveling is mostly vendor trash. Some Dropped set items and traited items have some worth to sell in the Guild Stores/Kiosks.
The best way to get what you want, as far as equipment goes, is to kill more mobs. Or, decon what you get and learn crafting. Or, vendor what you get and pay a crafter to make it for you.
Mob
An AI controlled monster. ‘Mob’ originally comes from the MUD era, where it was short for ‘mobile’, to differentiate monsters that would patrol a set of rooms as opposed to monsters which would stay in one place until killed.