If the “Link thumbnails to larger images” checkbox is ticked in the image settings, a thumbnail image and a larger image is automatically generated for product images. If unticked, only the thumbnail image is created.

Images with filename starts with t_  are product thumbnails. When an image is added to a product, the image file is sized down to the thumbnail size defined for the product style. This thumbnail file begins with t_. If the image file dimension is smaller than the thumbnail size defined for the product style, the thumbnail image file is not resized, and will not have t_ prepended.

Images with filename starts with l_   are product larger image. When an image is added to a product, the image file is sized down to the “Maximum size of linkedlarger image” setting. This larger file begins with l_. If the image file dimension is smaller than the setting, the larger image is not resized, and will not have l_ prepended.

Images with filename starts with k_  are link images. Each page and product can have a link image. Link images are created when the “Page/Link to other pages or products” or “Product/Cross promotions” dialogs are used to create a PageLinkBox or ProductCrossPromotion. These image files begin with k_.