Help:Templates
A template is a page created explicitly for transclusionhttp://en.wikipedia.org/wiki/Wikipedia:Transclusion - the MediaWiki process of including the contents of one page within another page. Any page can be transcluded, but templates are designed specifically for that purpose, usually for repetitive material that might need to show up on any number of Wikimedia articles or pages. They are commonly used for boilerplate messages, designs, standard warnings or notices, infoboxes, and similar content. Templates may contain plain text, wikitext, HTML and/or CSS, or even other templates, and they have some limited programming capacities: customizable values (called parameters), calculation and branchings (using parser functions), and access to wiki-specific variables (magic words), such as dates, times, and page names.
To use a template in an article or page, a template tag (always of the form Template:Template name; the name of the template enclosed in doubled curled brackets) is added where you want the template to appear. When a reader wants to view the page, the Wikimedia servers fetch the contents of the template page, make any calculations that need to be made, and then replace the template tag with the newly processed contents of the template before sending the web page on to the reader's browser. From the perspective of a reader, a template looks as though it were written directly into the HTML of the page in question.
Creating, Editing & Using Templates
Creating a New Template
You start a new template in the same way you would start a normal page. The only difference is that its title must be in the form of Template:templatename.
Once you have made the template, you can add Template:Templatename to the pages you want to use it on. Every page using this template will get the same boilerplate text, each time a user visits it. When the template is updated, all pages containing the template tag will be automatically updated.
Editing an Existing Template
If the template you want to edit looks like Template:Foo, you would go to Template:foo to edit it. To get there, type in the URL to your address bar, search for it, or make a link in the sandbox and click on it.
Once you are there, just click "edit" or "edit this page" and edit it in the same way you would any other page. You can add anything you would add to a normal page, including text, images and other templates. Please be aware that your edit might affect many pages, so be cautious.
