From @Mithgol on Tue Sep 15 2015 11:02:05 GMT+0000 (UTC)
A portable application is the one that is designed to run on a compatible computer without being installed in a way that modifies the computer’s configuration information. Such application can be stored on any storage device (including internal mass storage and external storage such as USB drives) – storing its program files and any configuration information and data on that storage medium alone.
I imagine some users would want to have the same local storage (and pinned media) at home and at work by bringing a mere USB stick where full BYOD is not practical.
Copied from original issue: https://github.com/ipfs/faq/issues/33