An instance is pocket zone within the game world. It allowes multiple groups to go through the same area at the same time without having to share the area.
To make things a bit clearer, it's a copy of a certain zone specifically for you or your group. Nobody else can enter your zone but they do get an exact copy of it for themselves.
Advantages of instancing are lighter server load (which translates to less lag) and there's nobody to deal with, such as griefers, campers, killstealers, etc... On the flip side of that, you also don't get to meet new people or receive/give assistance, etc...
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An instance is pocket zone within the game world. It allowes multiple groups to go through the same area at the same time without having to share the area.
To make things a bit clearer, it's a copy of a certain zone specifically for you or your group. Nobody else can enter your zone but they do get an exact copy of it for themselves.
Advantages of instancing are lighter server load (which translates to less lag) and there's nobody to deal with, such as griefers, campers, killstealers, etc... On the flip side of that, you also don't get to meet new people or receive/give assistance, etc...
Spawning a new instance can be based on other things too though. Such as total number of people in the zone (such as a newbie training areas).