Use attributes and attribute groups to create different variations, models, packs, etc. of a product. Attributes need not describe just physical differences between models; for example, not only do you use attributes to sell a T-shirt that comes in 3 colors (blue, white, and red), you can also create different volumes which you can then sell at digressive prices (one piece at base price, a pack of 5 for 5 euros less, a pack of 10 for 15 euros less, etc.).
