Each crew member is different and you, the captain, will face many different challenges while managing the ship and crew in battles or events. Let me try to explain it in a quick FAQ.
What makes each crew member different?
Each crew member will have skill stats as previously mentioned and each skill will affect your ship performance, additionally to the standard skill knowledge each member may have a few traits.
What is a trait? and how will that affect my ship?
A trait is a personal characteristic to each crew member, maybe one or more will be assigned to each member. For example, a crew member may be fearless and greedy, and this will translate while playing into many different actions, being fearless means never runs and may lose loyalty points if the captain decides to run from battle, so when boarding ships this crew member will fight until death and won't be scared and run in panic when health is low. Also the greedy trait means that there will be a request to raise the salary paid every few missions or he/she may lose loyalty points overtime, also may lose loyalty points when certain options are chosen like not risking the ship for an incredible loot in an dangerous asteroid field. So traits will have real impact on each crew member and how the ship operates.
How many traits are you planning to have?
At the moment there are more than 20 traits, like Benevolent , Greedy , Diligent , Lazy , Fearless , Coward , Educated , Inexperienced , Efficient , Incompetent , Flexible , Stubborn and many more. Each with bonuses and penalties.