I have heard USP used two ways: unique selling proposition, or unique selling position; I am not sure that it really matters. What really matters is what sets you apart from your competition. Sometimes, this takes some digging and intense shoveling to get to the bottom; the roots and the foundation. This is usually very difficult in a commodity market. Why should your client buy toilet paper from you? You can buy toilet paper anywhere. Is it the price? Price does not make you different; everyone can negotiate price. Is it your free delivery? Everyone offers "free" delivery. Is it your charming personality? Or is it your extra soft, extra absorbent, bio-degradable material that turns into money? 

Brand can encompass logos or symbols, name, slogans or taglines, a musical jingle, a color scheme, packing designs, staff demeanor or uniforms. Brand Identity is important because it connects you to the marketplace, sets you apart from competition and helps consumers make decisions. How do you develop identity? Have a clear and consistent message and make sure you keep your brand in front of your prospects and clients. Brand is the whole enchilada; identity is having it picked out of a line up. 

Your brand should connect you to the market place: your audience. It should set you apart and differentiate you form the competition. The Brand should imply what you offer and who you are. The Brand also helps people make decisions. And, Brands can become assets. After it was all said and done, Circuit City still sold its logo/brand for 7 million. BCBG, a high end women's clothier, used its brand for collateral for a 54 million dollar loan for product growth. Contact a business attorney to learn more about the legal benefits; consistency is key when there is a potential issue over usage and first rights.