NPC -> Non-Playable Character, like the gunsmith. I do not have time to go into an in depth explanation as to why trading with an NPC is a much better way than player to player trading (which brings in the Free Market System in to the gameplay, which is known to have corrosive effects on how games are designed to be played - look at recent FIFA events for example). However, when trading with an NPC, Bungie could create a restricted market which if implemented properly could allow for it to restore a form of fairness to the game by eliminating the problem with outliers (people whose "bad luck" place them far outside the normal distribution of the RNG curves - say 6 or 7 sigma). By controlling the market Bungie could give greater rewards (other than just gun parts) to people who turn in high valued weapons/armor while only "re-selling" those items to people who are outliers in the activities that give those rewards (want a "Fatebringer", then you have to run VoG multiple times before becoming eligible to buy it - showing that you are an "outlier"). Let's face it, the RNG system is inherently unfair since not everyone can be treated equally, but by bringing in a pseudo-market Bungie could address the inequalities of the RNG system to reduce the impact on the outliers while both making sure the games goals are achieved while relieving the frustration of those that feel like the game is biased against them, regardless of their skill and effort (since by definition RNG systems do not reward for either skill or effort).