Nendaz is one of the smaller resorts linked to Verbier to make up the 4 Valleys ski network. It is a largely purpose-built, apartment-dominated village and is a fair bit quieter than Verbier. It also has the reputation for being a fair bit cheaper. Combined with Verbier, Thyon, Siviez and Veysonnaz, there's a total of 400km of pistes. The town is undistinguished, but it does have sufficient amenities for holidaymakers, with ice-skating, plenty of cafés and restaurants, a good ski school and childcare facilities. The skiing caters mostly to beginners and intermediates, but there is extended domain to explore for more advanced skiers. In particular, experienced skiers will love what Verbier has to offer, but the journey from Nendaz can be complicated.
Overall, Nendaz is a quieter and cheaper option than Verbier, but the Swiss concept of 'cheap' is a little at odds with that of many skiers. Nendaz does provide everything you need, including most of the delights that its bigger brother offers.