The short explanation
Every setting returns to how it left the factory. Because that is destructive, devices usually ask you to confirm deliberately — typing a word rather than clicking once.
Where you run into it
Two situations make it the right move. After a firmware update that leaves something behaving oddly, a reset clears any setting that no longer means what it used to. And when a wrong network address has made the device unreachable, a reset from the device's own controls is the way back in — no network required.
Export your configuration first if you have one worth keeping. A reset is not reversible.
How the DR HDMI 8K handles it
The DR HDMI 8K has two separate resets on the CONFIG page: RESET TO FACTORY DEFAULTS for all settings, and EDID FACTORY SETTINGS for the EDID configuration only. Both need the word RESET typed in to confirm; the full factory reset also needs a power cycle afterwards. A reset is also available from the OLED menu on the unit itself, which is the route back from a wrong static IP.
Want to test your own HDMI chain?
The DR HDMI 8K is sold through the HDFury.eu web shop.