From Ars Technica:
The Security Keys are based on Universal Second Factor, an open standard that’s easy for end users to use and straightforward for engineers to stitch into hardware and websites. When plugged into a standard USB port, the keys provide a “cryptographic assertion” that’s just about impossible for attackers to guess or phish.
This appears to be a more sophisticated version of dongles that were popular for a while as a method of confirming that people using software actually had a license.
This added security could be used by dental offices that use remote access. For example an administrator making after hours calls, a bookkeeper doing the accounting from a remote location or a dentist doing notes and treatment plans at home.