VisualEditor, the visual interface to edit wiki pages, includes a tool to easily edit templates. However, in order for that tool to be most useful, it needs to be able to pull information about the template; mostly, it needs a list of possible parameters for the template, and their characteristics.
|Without TemplateData, each parameter needs to be added manually when inserting a new template.|
|No information is provided about what the value of the parameter should be.|
|With TemplateData, a list of supported parameters (and their description) is provided for the template.|
|TemplateData provides context for each parameter, and makes it much easier for users to modify templates.|
One of the things we need volunteers to do is the adding of TemplateData to templates (particularly high-profile ones, such as infoboxes) so that they are easy to edit.
The TemplateData help page explains how to add TemplateData information to a template.
You can probably think of some pretty important templates on your wiki very easily; experienced users know pretty well which templates are a big deal, and will inevitably find out when they try to use them and discover there isn't any TemplateData.
You can find an automatically-generated list of most used templates on your wiki on the Special:MostUsedTemplates special page. If you're interested in obtaining a copy of that list in wiki format (easier for collaboration), we can build that list for you. Please send your request by e-mail to okeyes-at-wikimedia-dot-org.