If you are here you are new, so templates are stuff that replace stuff in a wiki, example:
(note: {{USERNAME}} replaces itself with the user watching the page and {{PAGENAME}} replaces itself with the name of the page your on)
There is a template named Cool that in it there is: {{USERNAME}} is cool
If you type {{Cool}} you get: <insert name here> is cool
The name will be differ for everyone. Now the basics:
Making a template[]
To make a template, first, make a page with this name: Template:Name of template
Then type the contents of it and at the end, write <noinclude>{{Documentation}}</noinclude> and note that there in ONLY source mode in templates.
Categories[]
Categories are good to put in templates. When editing, write [[Category:name of category|{{PAGENAME}}]] to sort that page into that category.
Test[]
Make a template that has a category to Contents in it. When done, send the template page to me.