256 colors or 8 bits is still popular for most home use. In fact some games will not play well on any other. Check with the vendor. 65,536 colors or 16 bits is great for video and desk top publishing. Like a TV set, you measure the size diagonally.
Larger ones are for commercial use.
If you look closely, you may see some tiny dots on the screen. The closer the dots are, the sharper the image. Buy a monitor with at least 0.28mm dot pitch or less. This determines how much can be seen. Lower resolution displays a larger area of an image.