What are 8bit and 10bit videos? Which video should I download for a better experience?

Problem
Recently I tried to download a video from a media sharing website. I look for the best quality video file. There are different uploader they upload the same video of different file size. In order to get the good quality file for lowest file size, I check screenshots of video and file description. There I find that one file is 8bit and another one is a 10bit file. The screenshots for them looks same. What is the 8bit video and 10bit video mean? Which one has higher quality?

Answer
The term 8bit and 10bit are used to representing the color depth of video file. It is actually a measurement to how many possible individual colors is in the video frame. The primary color shown on screen are Red(R), Green (G), and Blue (B). Bit depth is the number of bits used for each color (either R, G, or B) component of a single pixel

For example for color R, 8bit image uses 8 bit to represent color R in a single pixel.
In 8 bit, it can produce 28= 256 shades of color R. similarly it produce 256 shades of green and 256 shades of blue in a single pixel. Then the total number of variation of color is equal to 256 x 256 x 256 = 16,777,216. An 8bit file can show roughly 16.8 million individual color.

A 10bit (210=1024 color level) file shows 1024x 1024 x 1024 = 1,073,741,824. Roughly 1.07 billion possible distinct color.

So the color gradient in 10bit video will be smoother than 8bit. But for human eye, the difference between 8bit and 10bit is very hard to notice and most of the conventional display support 16M colors only (8bit). So it is not an important factor for a regular guy.