The PARA Method is “a universal system for organizing digital information”. As such it forms part of Tiago Forte’s online course, Building a Second Brain (sign up for the course here, watch a short introductory video here, read an overview here).
The links above give information by the creator of Building a Second Brain (BASB) himself, so I won’t summarize it here. I’ll just briefly point out a key element of the PARA system as I understand it just from reading some articles and watching a few videos. I’ve been putting it into practice and finding it very useful.

P.A.R.A. stands for Projects — Areas — Resources — Archives

Archive is self-explanatory, as should be resources, though in PARA it seems to be more encompassing than “project support materials”.
It’s the distinction between Project and Areas of Responsibility that I found most enlightening and useful.
If you’re a GTD-er, you’ll be familiar with Areas of Responsibility – the 20,000 ft level or horizon, just above “current projects” – which forms part of the Horizons of Focus: ” The GTD Horizons of Focus is a framework for how to align your daily actions with your visions, goals, and life-purpose. Done right, it will place you in the captain’s seat for controlling the most important aspects of your life.“
Forte’s Areas of Responsibility seems to me the same as the GTD one.
A project is “a series of tasks linked to a goal, with a deadline.” An area of responsibility is “a sphere of activity with a standard to be maintained over time.” … even the smallest confusion between these two categories is a deeply rooted cause of many personal productivity problems.
A project has a goal to be achieved… by a specific moment in time. It has a deadline or timeframe. …
An area of responsibility, by contrast, has a standard to be maintained. And there is no end date or final outcome. Your performance in this area may wax and wane over time, but the standard continues indefinitely and requires a certain level of attention at all times.
The PARA Method: A Universal System for Organizing Digital Information
People often mistake their areas of responsibility for projects. They’re not. Projects have defined deadlines; areas continue indefinitely and require attention and adherence to standards.
There are three absolutely critical things you cannot do unless you break out your areas of responsibility into clearly articulated projects. The first is that you can’t truly know the extent of your commitments.…
Second, you can’t connect your current efforts to your long-term goals…
Third, you can’t know if you’re making progress toward your goals.
The PARA Method: A Universal System for Organizing Digital Information
The other useful tip I learned from this article was, once you’ve setup PARA in your note-taking application or your To-Do app, recreate that same setup across all your relevant digital programs. This takes time, but I’ve made a start syncing my YT playlists with my bookmarks and my Evernote notebooks. It makes so much sense and saves time in the long run.

Here’s why this is important: you will always need to use multiple programs to complete projects… but technology is advancing too quickly on too many fronts for any one company to do every single function best.
Instead of … looking for “one platform to rule them all,” formulate your Project List and then replicate that list across every single tool you use, now and in the future… down to the exact same spelling, punctuation, and capitalization, so that your transitions between programs are as seamless as possible.
…people tend to use different organizational schemes in every program they use… forcing their brains to “load up” and remember a different one every time they switch programs.
The PARA Method: A Universal System for Organizing Digital Information
The article ends with a simple exercise that helps to understand the importance of clearly distinguishing projects from areas:
There is a very illuminating exercise you can perform once you’ve taken the time to formulate a clear Project List. Put it side by side with your Goal List, and draw lines matching each project with its corresponding goal.
The PARA Method: A Universal System for Organizing Digital Information