I need help understanding VGA pin out?

Question

i understand most of the pins on a VGA cable but i need help with a few

Pin (9) is called a key what does that mean and whats its function?

Pin (12) is ID1 or SDA i dont understand the function of this

Pin (13) HSYNC

Pin (14) VSYNC

Pin(15) ID3 or SCI

arent vga conections just like RGB or component conections?

Answer 1

You will find your answer here

http://pinouts.ru/Video/VGA15_pinout.sht...

Answer 2

pin 9 not connected so no function

12 is Monitor id bit 1

HSYNC is Horizontal Sync signal

VSYNC is Vertical Sync signal

ID3 is Monitor ID bit 3

ID Bits are used to identify type of monitor you have connected to cable.