The Launchpad development team uses User stories to describe its user requirements.
User stories are in the form:
As a <user role>,
I want <feature description>
so that <benefit to the user>
It describes succinctly who the feature is for, what it is about and what is the benefit of it to the user. We find that last part especially important as it usually provides more depth to understand what the feature should achieve.
User stories are very effective tool to help plan features because they are cheap to write and maintain. You don't have to invest a lot of effort into writing details for something that might eventually not be worked on for some time when a lot of things will have changed anyway.
They serve as a conversational basis in understanding the feature. On this wiki, most stories will have a Notes section containing some notes and information that was gathered when discussing the story.
Epic / MMF
Not all user stories represent the same scope. The team usually starts by writing some very high-level stories that some call Epics.
These are used for long-term planning and will be broken down into smaller stories that can actually be scheduled and delivered within a cycle. When breaking the "Epic" into smaller stories, we try to focus on the essential components of the epic. That is, in that process we should consider the epic like a "Minimum Marketable Feature". (See also More insights on epics vs mmfs)