I take Zero credit for coming up with the idea.
Here are some links if you're interested in learning more about this "Second Brain" + "Public Learning" stuff:
P -> Project is “a series of tasks linked to a goal, with a deadline.”
Examples include: Complete app mockup; Develop project plan; Execute business development campaign; Write blog post; Finalize product specifications; Attend conference
A -> Area of responsibility is “a sphere of activity with a standard to be maintained over time.”
Examples include: Health; Finances, Professional Development; Travel; Hobbies; Friends; Apartment; Car; Productivity; Direct reports; Product Development; Writing
R -> Resource is “a topic or theme of ongoing interest.”
Examples include: habit formation; project management; transhumanism; coffee; music; gardening; online marketing; SEO; interior design; architecture; note-taking
A -> Archives include “inactive items from the other three categories.”
Examples include: projects that have been completed or become inactive; areas that you are no longer committed to maintaining; resources that you are no longer interested in