It's what puts graphics on the screen. If you are not interested in hacking or developing it, there's not much else to know except X11 is deprecated and Wayland is not finished, leading to this suboptimal situation.
But at the same time it makes me a little sad. Part of the draw of Linux was being able to understand what was under the hood and how to bend it to your will.
I’m hope the community doesn’t lose sight of that in trying to gain new users.
People often talk about the year of Linux or what success is, and in my opinion, Linux had achieved success by 1996.
Trying to pull a casual user from windows or Mac OS is a worthy goal, but that shouldn’t be the end all be all metric.