What is a "scan" in VGA programming?

Question

I've been reading this reference: http://www.osdever.net/FreeVGA/vga/vgafx.htm to learn VGA programming, but because I'm a student that just started learning about low level programming, I find it hard to understand. What does it mean when the reference says "scan"?

Especially in the "Split-screen Operation" section in the article, I'm not sure how "scan" is related to splitting the window.

I'd appreciate it if someone can explain briefly or link me to another reference where I can learn about it.

Answer 1

A Scanline is a single pass across the screen horizontally.