Visual Downloader is a download tool that allows Joomla! administrators to associate an image with a downloadable file so that users can preview what they are downloading.
Visual Downloader is packaged as a .zip file, which can be installed using the standard Joomla! installation tool.
Once you have installed Visual Downloader, you can create categories and sub-categories for your downloadable files. When you create downloadable files through the Visual Downloader downloadable file manager, you assign each of them to one of the categories you have created. If you upload an image preview file for a particular download, that image preview will be associated with your download file to give users a preview of the file(s) they are downloading.
Visual Downloader exists as a Joomla! component. It can be linked to as a Joomla! Menu Item Type. When this method is used, the menu item links to a page that includes all of the downloadable files you have created. If you want to create a link to a Visual Downloader category instead, you would need to change the Menu Item Type from Internal Link->Visual Downloader to External Link and insert the URL of the Visual Downloader category you want to link to, for example: index.php?option=com_download&view=download&cid=[categoryId], where categoryId is the id of the category you want to link to.