sRGB colorspace is a complex subject that involves understanding how monitors display color, how pictures/movies are stored and also how the limited precision of 8-bit images are handled to store color information more efficiently.
Some articles that help explain sRGB: https://www.cambridgeincolour.com/tutorials/gamma-correction.htm https://en.wikipedia.org/wiki/SRGB
Generally monitors don't display pixel values linearly. There is usually a curve to how much the brightness changes vs. the pixel's color. Many monitors use the sRGB curve as their outputs.
This article is not yet finished