What is instancing?

I know this isn't about Guild Wars directly.. but I've seen this referred to in some threads around the place, and I admit I don't seem to be too familiar with it..

I'm not sure what it is or does.. so if someone could please explain it to me? Or at least point me to a link which explains it... would really appreciate it!

As I said, I've seen this term in a few threads in the forum, as well as some people asking for it to be put into GW... and would love to know what the hell they are talking about.

you and your group get your own separate *instance* of that map be it a mission an explorable area etc.

nobody can join you there or pk or loot steal gank or cause trouble

the only place you can interact with a crowd is in towns or outposts

But isn't that exactly what GW has already? Or am I confused?

I guess I'm confused because after reading a thread in the suggestion's forum and someone asking for "instancing" to be put in the game.. and then someone saying GW wasn't made with that in mind...

http://www.guildwarsguru.com/forum/s...ad.php?t=52912

but if what your saying is right.. don't we already have what he's asking for? I don't know ;/ (lol that's why I'm asking)

That's saying no instancing? but isn't it when you enter a explorable zone and/or mission each area is created seperatedly for you & your party called instancing? or is the other poster asking after something else?