A modification (also called "mod" or "package") is package of files meant to be used to modify the files of an SMF forum. modification packages can be installed using SMF's Package manager. meant for a new or enhancing package for SMF forums. Mods are created with PHP (PHP: Hypertext Preprocessor and/or HTML (HyperText Markup Language, can include JavaScript and CSS (Cascading Style Sheets)), and can be installed using SMF's package manager.