Overview
When you need to determine the outcome of a character’s action, a player rolls a pool of six-sided dice. Only the single highest result matters; the rest are discarded.
Therefore, a larger dice pool is universally better than a small one. Players should always be aware of any means by which they can increase a dice pool (though some involve costs so it’s not always the best decision).
There are three types of outcome:
If the highest die is a 6, then the result is a full success. Things go really well and the character definitely succeeds at what they set out to do. If you roll more than one 6, then the result is even better—it’s called a critical success and the character will get an even greater advantage.
If the highest die is a 4 or a 5, then the result is a partial success. This means that the character will basically achieves what they set out to do, but there’s some kind of consequence associated with it. More trouble, harm inflicted, reduced effect, etcetera.
If the highest die is a 1, 2 or 3, then the result is a bad outcome. Things go really poorly. This doesn’t mean a character necessarily fails, but if they want to succeed it’ll hurt somehow. It will involve hard decisions; in most cases the cost will be too great, and so the character won’t achieve their goal and will still suffer complications, too.
If a character’s dice pool is zero for some reason (or even negative), then they can roll two dice and take the single lowest result. Note that it is impossible to roll a critical success with such a roll.
It is important for new players to know that even with larger pools, the most common result is 4/5, a partial success. Success at a cost, basically. Players should be encouraged to embrace the costs of their success, because more drama just adds to the story, even if it involves short-term pain. On the other hand, even one single die will offer a 50% chance of some sort of success (ie. a 4/5 or a 6), which isn’t bad.
In the vast majority of cases, dice pools will be made up of:
a skill rating like attune or scrap
an attribute rating such as prowess or resolve
a ship's crew quality
the wealth of the system the Crew are currently in
You take up dice equal to this rating, and may have extra dice from various abilities or circumstances. And then you roll them to see what the outcome is!
More information on the type of dice rolls characters can make is available here.