These days, most people coming to Bali stay around Kuta beach, with its big waves for surfing, big hotels, night life and crowds of people. But Bali is a big island with many beaches, each with its own special character. The first of Bali's beaches to be developed as an international resort destination was Sanur, and you couldn't find a beach that is more the opposite of Kuta.
Sanur lies on the east coast of south Bali, facing the rising sun. A reef about 100 yards from shore causes the waves to break and dissipate quickly, so instead of Kuta's big waves, at Sanur there is often little more than a gentle lapping of the waters on the beach. The gentle waters between the shore and the reef are excellent for swimming, wind surfing and paddle boating. When the tide goes out in the afternoon, it exposes a large area of sea grass interspersed with tide pools that can provide endless fascination if you're in the right frame of mind.
The beach itself at Sanur is generally wide and flat. There are many small jetties along the beach to help preserve the beach. Unlike Kuta, you will find many beach activities at Sanur, such as volleyball or just plain sun bathing. Also unlike Kuta, you'll find many hotels, shops and restaurants right on the beach. At Sanur, it's entirely possible to sleep, eat and shop without ever losing sight of the ocean. Of course, the most often remarked difference between the two beaches is Sanur's general lack of night life compared to Kuta. While Sanur doesn't have the big clubs you'll find around Kuta, it does have many pleasant restaurants and pubs where you can spend a nice evening.
I suppose you could say that while Kuta is "all about the party" Sanur is "all about the beach."