From Rosetta Code

Library: [[:Category:{{{1}}}|{{{1}}}]][[Category:{{{1}}}]] version {{{2}}}

This template is for tagging solutions by the libraries they use. It adds both a link to the page for the library and a category of the same name. It also documents the version that this was tested with; that second parameter may be omitted.

This is a template. There are many others. See Category:RCTemplates for a complete list of templates.