PARA stands for: Project Area Resource Archive
The different categories can be determined based on Actionability.
Projects are the most actionable and have a deadline.
Areas are typically areas of responsibility. Things that have to be, or have standards that need, maintained. There is usually some from of consequence without.
Resources are information that are generally useful. Useful to others, or useful for other interests, but have no consequence if not maintained.
Archive is where projects/areas/resources live that are no longer active.