What the numbers mean
Screen resolution is your display size in CSS pixels, the unit websites use. Multiply it by the device pixel ratio to get physical pixels: a 1440 × 900 screen at a ratio of 2 is a 2880 × 1800 panel. Windows display scaling and browser zoom both change the ratio, so press Ctrl + 0 (⌘ + 0 on a Mac) to reset zoom before reading it. The viewport is the part of the window a web page can use.
Refresh rate test
The live Hz figure counts how often your browser draws a new frame. If a 120 Hz or 144 Hz monitor shows 60 Hz, set the refresh rate in your system display settings, use a cable and port that support it (DisplayPort or HDMI 2.0 and up), and turn off battery saver. Laptops on battery and some browsers lower the frame rate to save power, and a busy CPU can make the reading dip for a moment.
Is anything sent anywhere?
No. The page only reads what your browser already reports, and nothing is stored or uploaded. Use Copy all to paste the details into a bug report or a support chat.