The Product Feeds add-on allows exporting products to popular comparison shopping websites (also known as shopping engines and price comparison websites). The add-on does it by generating data files (product feeds) that list all of your products in a specific format.
The add-on supports the following shopping engines: Nextag, Pricegrabber, Shopzilla, eBay Commerce Network (shopping.com), and Google Shopping.
The product feed format depends on the shopping engine, but the popular ones are XML (extensible markup language), CSV (comma-separated values), and TSV (tab-separated values). You can edit CSV and TSV files in spreadsheet programs like Microsoft Excel, LibreOffice Calc, and Google Docs.
Many price comparison websites require fields that are not typical for X-Cart, so the add-on leaves them empty when generating product feeds. That is why the files you get out of this add-on are a good start, but not something you should automate all the way to your shopping engines. Instead, you should manually analyze and edit the automatically generated product feeds in a spreadsheet program for the most effective results, better sales, and ROI.
Also, some engines require that you supply additional information on your products: color, size, age group, and so on. You can do that by defining product attributes in the X-Cart back end and using the field mapping section on the feed settings page.