@jeffreywsnyder In terms of optics, “resolution” is a measure of the smallest distance over which you can distinguish two points.
In terms of these projectors, it is a measure of the number of pixels used to create the image.
A poorly-focused image will, of course, have poor resolution in the optical sense. However, the number of pixels puts an upper limit on the image resolution, regardless of focus.
@jeffreywsnyd Resolution describes the number of individual colored dots (pixels) that make up the displayed image. Native resolution is a physical characteristic of a device, and it means in this case the device can produce 480 rows of 854 pixels.
The resolution doesn’t change with the screen size, and that’s why the image looks worse when it’s bigger. This is generally expressed in PPI, or Pixels per Inch. At 42" (small by modern TV standards), this device displays only 23.33 PPI. At 120", that drops to an abysmal 8.16. For comparison, a 42" 4k TV has 104.9 PPI.
These kinds of projectors are okay for casual movie watching or whatever. I guess if you constantly find yourself wishing your phone screen was huge and blurry when you want to watch a movie in a place with no TV, it’s a good buy?