How is this FAQ organized?

As much as possible, it is organized by solar system object as one progresses outward from the Sun. For each object, there may be some questions which may be specific to only one planetary mission which has visited that object as well as those which are pertinent to the object in general. In those cases, there are subheadings under the object to specify whether the question is a general (not mission specific) or mission-related question.
In some cases, a given question may apply to the data from more than one object (for example, because a mission went to several planets/objects) or is a more generic questions (for example, about planetary geology or atmospheres). Answers to these questions may be found under the General category at the top of the FAQ.