Sitecore Taxonomy module. This module allows you to classify the content on your site by applying tags to your items which later can be used to search through.
Installation Install "/Data/packages/Taxonomy module.zip" package to apply Taxonomy module to your Sitecore website. Another way is to install "/Data/packages/Taxonomy module.Items.zip" package, fetch the project into the Website folder and build it.
For additional information check the http://marketplace.sitecore.net/en/Modules/Taxonomy.aspx.