ScreenlyOS runs on our own hardware, a Raspberry Pi, or a Sharp display. Plenty of screens run on something else: a Samsung or LG commercial display, a ChromeOS device, an Android stick.
Screenly Anywhere is how you bring those screens into Screenly. It runs as software on top of the operating system the device already has, so hardware that cannot take ScreenlyOS can still be a Screenly screen.
These pages cover what it is, why you might choose it, and what you trade compared with ScreenlyOS.