Since a lot of people here don't seem to know about Second Life I figure some introductory materials can't hurt in case anyone decides to try it.

Second Life is made up of so called regions, each of them is a square 256m to a side and 4096m high as far as building is concerned. In theory the water level can be set to different values in each region but the most common is 20m, especially for the connected mainland regions where it has to match for the water to look connected between adjacent regions.

Inside a region there are coordinates x (low=west, high=east), y (low=south, high=north) and z (low=down, high=up).

Each region runs on a separate simulator (modern servers might host more than one simulator but it is separate processes) so crossing or teleporting into another region requires a handover. If regions are crossed in quick succession, especially with high latency connections, this can lead to crashes or falling off a vehicle.

The regions themselves are placed on a grid with x (again, low=west, high=east) and y (low=south, high=north) coordinates. The first region Da Boom around which the mainland grew has coordinates 1000, 1000. The coordinates can be shown in the viewer but the regions are more commonly addressed by their region name.

Spots on that coordinate grid that do not have a region show as an endless ocean (even if there are regions behind it you can not see them) and you can not enter them.

This coordinate grid has lead to Second Life expressions like "on the grid" for things happening on SL.

There are different types of regions with different performance characteristics, agent (avatar) limits and land impact (LI) limits for building and other objects. LI is often also referred to as prims by old time SL users since it used to be a limit in the primitives (cubes, spheres,...) that used to be the only way to build but since mesh objects were added the more general term land impact is used.

The Second Life mainland has a number of continents, almost all of them are part of a continuous area of connected regions. The major exception is Zindra, the adult continent.

Since this post is already quite long I will perhaps introduce the continents in a future post in detail. Hopefully this information will be helpful to some people.