In Everquest 2, Mods and Addons have a very special role in adjusting the user interface (UI) to players' specific needs or preferences while playing the game. Mods, also abbreviated as modifications in Everquest 2, act like a third-party addition that helps players greatly change or improve some aspects of the Everquest 2's user interface.

Mods, sometimes called User Interface Modifications (UI Mods), in general can do a wide diversity of main tasks in the game play. They can be used to add a set of new buttons to the players screen, change the built-in player and party frames or automate some aspects of spellcasting as well.

In certain cases, mods can totally be a tool supplementary to the standard Everquest 2 user interface that generally provides users with much more advanced and varied functionality.

Addons are exactly the same as Mods, the only major difference is just in the matter of their names. Normally "Mods" tend to mean smaller things that merely modify existing functionality of the user interface, while AddOns are more likely to add extra functionality to the user interface.