Quest letters are the way that GMs can tell how you did on a quest. We only have quest letters for quests that are on the wiki. Here is an example of how they work:
Question 1: A or B?
Question B: A or B?
That makes the quest letters "ba"
When you finish a quest on the wiki, look at the address bar. It should say http://scifirpg.wikia.com/wiki/[questname]/[questletters]. If the last page in a quest doesn't say what your quest letters are, you can look at the address bar and find out.
NOTE: If you lie about what your quest letters are, you may be facing a temporary ban from the game.