Javascript constructor (the same for all, so you do not need to think about it a lot);
XSL template. It defines visual appearance of the item. You can use built-in or create your own one. XSL files for built-in types are usually located in codebase/types;
CSS classes definition. By default css class name for top item element is created based on type name. using the following template: dhx_folders_[NAME OF TYPE IN UPPER CASE]_item. Thus if you use built-in type “ficon” and want to change something in CSS, you need to search for dhx_folders_FICON_item class in codeabse/dhtmlxfolders.css. If you create your own type (with name “mytype” for example), then define style through dhx_folders_MYTYPE_item class and sub classes