What is the difference between a CVT and automatic transmission?

They are completely different; there are no similarities between a CVT and a regular automatic transmission. The CVT uses belts and pulleys and is designed to alter the gearing to keep the engine running at a constant speed that delivers the best fuel consumption. A regular auto uses gears and hydraulics and the engine speed varies. There were some reliability issues with the CVT when they were first introduced, but these seem to have been sorted out and we see very few reports of problems with them now. The Toyota CVTs are as good as any.