Chaat is something unique to India. The name comes from the Hindi verb chaatna, which literally means licking. Basically the food that is so good that you lick your lips and fingers and utensils, that’s called Chaat.
It’s mostly fried food with lots of chutneys and spices, eaten as snack. Chaat is a popular street food because you quickly eat some chaat as a snack while shopping or site seeing.
There are at least a hundred dishes that can come under chaat from mildly spicy to very spicy.