Doom64 ex: Macros and macro control?

So I am making a Doom 64 ex map using the Doom builder 64. I messed around with it a bit ages ago but have limited experience with it. While looking at linedef actions I see something called macros and macro control. What exactly is that?

http://doom64ex.sourceforge.net/wiki/index.php/Macro_Scripting

Thanks for that!

Anyhow I have a new problem. For some reason switches don't animate. They still work, but the actual texture doesn't change.