Asti Spumante is not a Champagne, but a sparkling white wine from the Piedmont region of Italy. For a sparkling wine to be designated as Champagne, it must be made in the Champagne region of France.
Moscato is a close relation to Moscato d’Asti, but the main difference is that moscato is a still wine while moscato d’Asti is a semi-sparkling wine. Moscato d’Asti also does not go through a second fermentation in the bottle like moscato.
Asti and prosecco are both sparkling wines from Italy, with the main difference being where they are crafted. Prosecco is primarily from the Veneto region of Italy and made from the glera grape. Asti is produced in the Piedmont region and typically lower in alcohol (5-6%).
Moscato d’Asti is a sweet, lightly sparkling wine. When making Moscato d’Asti, the fermentation is stopped quite early, resulting in a sparkling wine that has fewer bubbles and is lower in ABV, typically measuring around 5-6%.