Magmi is a Magento Mass Importer developed as a magento DATABASE client, (ie not a magento extension) , that operates directly in SQL and is the result of a deep analysis of the Magento Database Model. The first magmi goal was catalog import & update. It can create products or update an existing catalog and deal with HUGE data (Millions of products could be managed by magmi,but even above a few 1000’s , you’ll see the real difference with dataSlow)