Help:Namespace
A namespace is a collection of pages which have content with a similar purpose, i.e. pages where the intended use is the same. Namespaces can be thought of as partitions of different types of information within the same wiki, and keep "real" content separate from user profiles, help pages, etc. [1]
Old School RuneScape Wiki namespaces
Forum
The Forum: namespace is used for Forum:Redwood Grove discussion pages.
Exchange
The Exchange: namespace is used for articles listing the current average market item prices on the Grand Exchange Market Watch. For an example, see here.
Update
The Update: namespace is for pages used on Template:Updates. They are also an archive of almost every update Jagex released. For an example, see here.
Calculator
The Calculator: namespace is used for Calculators to determine cost and experience based on current average market item prices on the Grand Exchange Market Watch. For an example, see here.
Module
The Module: namespace is used to house code for modules written in Lua (Wikipedia entry). For an examples, see here.
Template
The Template: namespace is used to house code for templates. For an example, see here.