How can a computer render a CLI/console along with a GUI?

Question

I'm confused when looking into graphics - specifically with operating systems.

I mean, how can a computer render a CLI/console along with a GUI?

GUI's are completely different from text. And how can we have GUI windows that display text interfaces, ie how can we have CLI in modern Graphics Operating system - that's what I'm mainly trying to grip on to.

How does graphics get rendered to display? Is there some sort of memory address that a GPU access which holds all pixel data, and there system's within OS's that gather the pixel position of windows and widgets, along with the Z Index and rasterize them to that memory address, which then the GPU loads to the screen?

How about the CLI's integrated with Graphics? How does the OS tell the GPU that a certain part of the screen wants to display text while the rest wants to display pixel data?