Doc:2.6/Manual/Preferences/Addons

The Add-Ons tab lets you manage secondary options which are not enabled in Blender by default. New features may be added with Install Add-Ons. There will be a growing number of such Add-Ons, generated by the Blender-community so look out for that one feature you were missing (or maybe simply create it yourself).

See the Add-Ons Page for more on using Add-Ons.