When a variant is added to the existing brand, it is called line extension. The variant can be anything from color, packaging, nutritional value addition, or a new shape. Line brand targets a subset of the consumers.
For example, Cadbury Bournville comes in three flavors − Raisin & Nut, Rich Cocoa, and Cranberry. Likewise Dairy Milk Silk comes in Orange Peel, Roast Almond, and Fruit & Nut variants.