Templates are used within articles to provide a consistent look to the messages placed into them. Changes to the look, wording, or style of the message can be implemented quickly, because templates are rendered for the reader when the article loads. Spaces in the name are allowed, e.g. {{original research}}. The first character (only) is not case-sensitive, so {{cleanup}} and {{Cleanup}} both work. This technique is commonly known as transclusion.
Templates in the article namespace exist only to help readers. These can include navigation aids, or warnings that content is sub-standard. Templates that provide information only of service to editors belong on an article's talk page.
An alphabetical list of every page in the template namespace is available at Special:Allpages.