They are basically that if an item is found to be not in a saleable condition (ie faulty) or not fit for the purpose for which it's designed, you are entitled to a refund or replacement at your discretion. What stores mean by that statement is they might offer something like a refund or exchange within 2 weeks if you change your mind about your purchase, but that offer doesn't have any bearing on your rights within the law. The Sale Of Goods Act is the one which explains all this in full.