There’s No Such thing as HDR, it’s all made up BS.
The actual industry wide Spec is HDR10.
Basically brighter brights and darker darks, and punchier colors.
Here’s the real Spec. Which is a little out of date, because new standards allow for Dynamic HDR10 which allows Light levels in a scene to shift in real time and maintain HDR10 standards. Like going from inside a cave and walking into daylight can go from blinding, and gradually normalize.
https://www.smpte.org/sites/default/files/section-files/HDR.pdf
It’s common knowledge that whenever someone says HDR. They are talking about HDR 10.