There are two ways to look things up in Wikipedia: by searching or by browsing.
If you know the name of an article for which you are looking, simply type it into Wikipedia's search box and press Go, or you can search for information on a topic by typing it in the box and selecting Search.
If you would like to look around the encyclopedia to see what is on it, use Wikipedia's Contents pages. Lists and indices are examples of contents for a published work, and Wikipedia has many of each, including a complete alphabetical index and indices by category. Links to all of Wikipedia's main contents pages are presented below, and they in turn link to the more specific pages.
Wikipedia's reference lists
Overviews of Wikipedia
An overview is a survey of what is covered in an area. Overviews of Wikipedia's coverage include:
Outline of knowledge—a set of outlines combined to provide a guide to Wikipedia's content. Each outline shows the structure of its subject and serves as a table of contents to its coverage on Wikipedia.
Overviews—a one-page outline of the contents of Wikipedia, covering 12 major subjects, providing links to key articles in each.
A portal is an introductory page for a given topic. It complements the main article of the subject by introducing the reader to key articles, images, and categories that further describe the subject. They also include to-do lists that are used mostly by Wikipedia's editors.
Wikipedia's main categorical index system is automatically generated from information (category tags) at the bottom of each article. The top-end pages of the category system are:
Categorical index – an index of major categories, arranged by subject – that section of the page is an exception to the category autogeneration rule, as it is crafted by hand.
Category:Categories—the highest level or "root" category in Wikipedia – its autogenerated entries are listed at the bottom of the page.