Prosecco is made from the Glera grape, which you can find on occasion as a still wine. To me, it's not remotely like Champagne other than that it is sparkling. Asti Spumante, the real kind, is more akin to Champagne. Asti of course is a town in northern Italy and spumante is the Italian word for sparkling (carbonated).
Now, you know the REST ..... of the story.