The virtual world can be accessed freely via Linden Labs own client programs, or via alternative Third Party Viewers. Second Life users create virtual representations of themselves, called avatars (also called Residents) and are able to interact with other avatars, places or objects. They can explore the world (known as the grid), meet other residents, socialize, participate in individual and group activities, build, create, shop and trade virtual property and services with one another. It is a platform that principally features 3D-based user-generated content. SL also had its own virtual currency, the Linden Dollar – which was exchangeable with real world currency.[5] Second Life is intended for people aged 16 and over. Built into the software is a three-dimensional modeling tool based on simple geometric shapes that allows residents to build virtual objects. There is also a procedural scripting language, Linden Scripting Language, which can be used to add interactivity to objects.