A 40 inch 1080p TV has a screen size of 40 inches diagonally and a resolution of 1920x1080 pixels. This means that the TV can display up to 1080 lines of pixels vertically, and 1920 lines of pixels horizontally, resulting in a total of 2,073,600 pixels on the screen.
A 1080p resolution is considered to be high definition (HD), but it is not the highest available resolution on the market. Nowadays, many TVs offer 4K resolution (3840x2160 pixels) or even 8K resolution (7680x4320 pixels) for even sharper and more detailed images.
The size of the TV is a matter of personal preference and depends on the viewing distance and room size. For example, a 40 inch TV is suitable for a small to medium-sized room, and the ideal viewing distance would be around 6 to 7 feet.