The Second Life world is made from prims (primitive shapes), these prims can be textured, adjusted and grouped together to build objects, buildings, pretty much

The Second Life world is made from prims (primitive shapes), these prims can be textured, adjusted and grouped together to build objects, buildings, pretty much anything. Each prim can have event driven, procedural scripts attached to them. There is basic RPC functionality available in LSL and objects can communicate with each other via chat channels, email (if I remember rightly every prim has a UUID and email address) or via a XML HTTP request. Prims can be programatically moved or altered, there is a system for drawing particles, rendering dynamic textures on surfaces and much later I believe surfaces became capable of rendering web documents on them. There is scope for a ridiculous amount of stuff. One of my favourite little projects was the Stargates you found on the grid, they all have unique addresses and work accurately just like in the show, they're pretty neat for getting around.