Are used for changing a bad result (i.e. the difference between hitting or missing a target, successful engine repair vs quick but leaky patch job, or living vs dying) or influencing the expected outcome of a situation...
...or something like that...
...pretty sure there's a more detailed explanation a few pages back in this thread.
Edit: Stolen from Roger's original post on pg 1....
What are Plot Points?
Note: Still not sure how this is going to work within an online game. This is the idea for the moment but I am open to suggestions.
Plot points are the characters chance to directly effect the outcome of the game. Everyone starts with 6 points, and can have a max of 12 at anytime. You expend plot points at any point in the game by adding a note at the bottom of your post or by PMing me.
Improve a roll: You call it before you do it. The number of plot points you use is the die you get to add (so 6 plot points equals a d6). For example, Wyatt wants to take out a Varmit with his gun. The Action is Formidable (15) due to cover. So Bromern says he is shooting at the man and added 6 plot points to his roll. So I would use his Agility + Gun Skill + d6 to roll his to hit roll, thus adding to the chances of being successful.
Save a Miserable Roll This is after the fact. You have failed on an action and you don't want that to happen. Each plot point you expend is equal to a half point of increase. In online game play, this is done by a post to Q&A or a PM asking if you can change that outcome. For Example, Sam needs to pilot the ship through a tight space. I post that he attempts the move but fails and does considerable damage to Rocinante. Eol asks if he can change the outcome. I look at what he needed (19) and what he got (16) and tell him he needs to expend 6 plot points to change the outcome.
Stay Alive This will be what you use them for the most. You can effect the damage done to you by expending points. Each 6 points gives you a d6 of damage reversed. For Example, Willow has been shot for 12 points of wound damage. She only had 10 life points left and she needs to stay alive badly. So she expends 6 points to get d6 life points back.
Manipulate the Story You can change the story with 1-3 points expended. It can only be a simple change, nothing that will throw of the entire plot. For example, you meet with a major underground figure and you need an in with him. Kora expends 3 points to make it that she knows this man from the past. Not close friends but enough to make an introduction possible.
How do you gain Plots Points?
Your Complications are meant to make things interesting for the characters. Playing your complications is the best way to get plot points. Allowing yourself to be flawed, to make mistakes and in some way advancing the story will bring you plot points. Allowing your character to succumb to their "greedy" flaw or speaking honestly when the situation calls for a lie are food for plot points. Not every time you use a complication will net you points, only when it is done to advance the story.
For example: Wyatt and his crew have finished a job to find their employer is now dead, and his killer is standing over the body. Mr. Killer offers Wyatt three times what the employer was offering to pay for their job, as long as they just walk away. The money is good, and it would go well into fixing a huge pile of troubles. But Wyatt has Straight Shooter (Honest) and Credo (Loyalty to Word) as complications. He looks at the body. He looks at the offered platinum. He draws his gun and shoots.
You also get points for completing challenges within the game, doing cool or interesting ideas that make the story fun or exciting.