In the simplest terms:
Trade system:
-Lvl 20 required
-Weapon or Armor for trade must be fully upgraded
-if faction specific must be rank 3 of that faction. same with vanguard.
-Item must be within class tier (Titan armor for Titan armor) (exotic for exotic) (DLC item for DLC item) (Blue engram for blue engram)
-Shards and energy trade must be 6 for 6. Materials must be 16 for 16.
-pay a glimmer fee for item deposit with post master. deposit item. add description from predetermined choices. (Ex. pay 7k glimmer, deposit Shadow Price, select auto rifle, scroll to new monarchy, select Vanquisher, wait for someone trading a Vanquisher, profit)
-player who traded item will appear under recent players if you want to send a thank you