World of Second Life
From Sl Wiki
The World of Second Life is made up of a large number of "parcels" of land. Most of these are united together to form 2 large land masses, or Mainlands. Residents may buy or rent parcels of land, allowing them to build, display, and store their virtual creations, as well as host events and businesses. It is also possible to buy islands, or "regions", separate from the Mainland, which offer greater control and security to the owners. The majority of companies and institutions setting up in SL tend to follow this route asthe increased security offsets the (usually) higher cost.
The combination of mainlands and islands results in a flat, earth-like environment that is simulated on a large array of servers, and is referred to as The Grid. Each server (running Debian Linux, for those into that sort of thing) is capable of running multiple copies of the server software. Each copy is described as a "simulation", hence the term "sim" is used to describe a region, whether it is an island or on one of the mainlands. It is worth making this distinction, as there is often confusion that Second Life is like the game, The Sims!
Virtual Real Estate companies like Anshe Chung (touted as the first US dollar millionaire created in Second Life) will supply land on both the mainland and separate islands, along with building services. However, many residents will acquire and develop their own land for themselves. Since Linden Labs owns all the physical servers, such purchases must be made from them.
