Those are interpolated frames. Like inserted frames. Its for smoothing out motion but can add artifacts and can look unnatural (soap opera effect).
Its marketing if anything. Like dynamic contrast that goes into the millions on edge lit LCD TV's/monitors. That takes the highest contrast level to the lowest, its misleading and in no way a replacement for native contrast or frames in this case.
Native refresh rates max out at 120hz on TV's. You want to look out for HDMI 2.1 as a specification as they are capable of doing 4k at 120hz.