css - Is it true that different devices choose which convention to use for defining a pixel?

Question

I'm reading about pixel sizes from the documentation here, and it says the following:

For a CSS device, these dimensions are either anchored (i) by relating the physical units to their physical measurements, or (ii) by relating the pixel unit to the reference pixel. For print media and similar high-resolution devices, the anchor unit should be one of the standard physical units (inches, centimeters, etc). For lower-resolution devices, and devices with unusual viewing distances, it is recommended instead that the anchor unit be the pixel unit. For such devices it is recommended that the pixel unit refer to the whole number of device pixels that best approximates the reference pixel.

What I Want To Know:

1) "For a CSS device": is a CSS device any device that can display an app that uses CSS? What would be an example of a non-CSS device? An old TV or something?

2) (main question) It says "for print media...the anchor unit should be...", whereas "for low-resolution devices...it is recommended that the anchor unit be...": I understand that the two options for anchoring the pixel are 1) make it relative to an inch, and 2) make it the reference pixel. So when they're making a given device, do they choose either (1) or (2) for px values for apps on that device? Like on an iPhone 1px might be the reference pixel, whereas on a TV it might be 0.75*(1/72) inches?

标签： cssuser-interfacepixeldisplay