To introduce new products in market, a seller can use an existing brand to do the same. This is known as brand extension. The new product could be from the same product category as currently served by the brand. Such a brand extension is known a line extension. The new product launched can also be launched in a different product category as well, and this is known as category extension. The brand line of a particular brand would consist of all the products under the brand, be it original or category or line extensions. Now, the set of all these brand lines offered by the seller would constitute the brand mix.
Unilever offers the brand Surf Excel in India that initially was present in the detergent segment. Line Extensions were gradually introduced line extensions with products like Surf Excel Easy Wash, Surf Excel Quick Wash, Surf Excel Matic Top Load etc. Further Category extensions introduced like Surf Excel Bar in the detergent bar category, Surf Excel liquid detergent in the liquid detergent category. The whole assortment of products under brand Surf Excel would be a brand line. However all the brand lines that Unilever offers like products Dove, Surf Excel, Sunsilk, Rin, Axe, Lakme etc. would constitute the brand mix of Unilever in India.