Instances Help

[Francis_4_Dead]

I've been neglecting the many uses of instances for a while (because I'm severely lazy); only now have I started to learn how to use them because I can't damn-right know how a Valve map works in Portal 2 with all the instances.

I'm starting to get the gist of it all, however. I'm currently toying around with them right now as I type this OP.

However, I want to know...
Is it possible or an instance to command another instance to do something? For example, say I want to have this portal-sensitive wall that would turn on a light bridge when a portal is placed on it; both the light bridge (for whatever reason) and the portal-sensitive wall was an instance. When I place a portal on said sensitive wall, is it possible for said wall to command the light bridge?

Thank you in advance.

EDIT: I also don't know how func_instance_parms work and what they do. If anyone can explain or post a video for me to watch about it, I'll gladly appreciate it!

EDIT2: I've noticed @ symbols in some names. What do these do?
Maybe I'm just horrible at searching, but I can not find any answers to these questions.