I've removed the require_tree line here, what it does is include every .js file in the directory. The '.' refers to the current directory, but you could add another line saying something like require_tree folder_name and it would go into that folder and include all of the .js files from in there.
It works pretty well but i prefer to be explicit about which files are included, and the current setup with that sharebox plugin requires it to be loaded after the DOM element which it is being applied to, so having require_tree . would result in it being loaded twice - once in the head section and once after the element in the body.