When interacting with neutral/friendly AI ships sometimes they will offer you a quest/challange, you cannot get these from station defender ships.
example: you hail a neutral hauler, and theres a unique quest such as-
Stay within a ion storm for X amount of time, reward is cash or diamond (ion mats)
Find lost loot in the scanner clouds, reward is cash or a free scanner block (forgot name)
Fight off a unique enemy that dwells within a energy cloud, can be 2 types- type 1 is a ship with no energy based weapons/shields, type 2 is a ship purely using energy based systems/weapons. you are not told what type, and there should be multiple of each type
and more, they shouldnt all be nebula focused just thought they where good examples