A new Cyanogen OS update is out and it brings about an exciting new feature, called Mods. But, before we dive into the story, one thing that always seems to come up has to be clarified - we are talking about Cyanogen OS, as found on some YU and ZUK devices, as well as the OnePlus One. CyanogenMod, while also making great progress and already utilizing Android 6 Marshmallow in its stable builds, is a whole other OS that the update in question does not concern. Now that that is out of the way, what are mods? Simply put, they are various third-party app features, baked right into the OS...
Source: http://www.gsmarena.com/cyanogen_os_131_update_is_now_out_with_new_mod_features-news-18747.php