Dynamic refresh rates have two main purposes: save power by only forcing the monitor to refresh when a new frame is available, and increase animation smoothness by synchronizing to draw rates (rather than "catching the next bus" at 16.67ms, on the 16.67ms, for 60 Hz monitors). Mobile devices prefer the former, while PC gamers are interested in the latter.
Obviously, the video camera nullifies the effect.
NVIDIA was first to make this public with G-Sync. AMD responded with FreeSync, starting with a proposal that was later ratified by VESA as DisplayPort Adaptive-Sync. AMD, then, took up "Project FreeSync" as an AMD "hardware/software solution" to make use of DisplayPort Adaptive-Sync in a way that benefits PC gamers.
Today's news is that AMD has just released an FAQ which explains the standard much more thoroughly than they have in the past. For instance, it clarifies the distinction between DisplayPort Adaptive-Sync and Project FreeSync. Prior to the FAQ, I thought that FreeSync became DisplayPort Adaptive-Sync, and that was that. Now, it is sounding a bit more proprietary, just built upon an open, VESA standard.
If interested, check out the FAQ at AMD's website.