A chiosco is a kiosk, like a food stall. A ristorante is a more upmarket restaurant, white cloth tables. A trattoria - literally a tavern - is a more informal restaurant. A rosticceria is a kind of Italian takeaway place. They cook traditional Italian food, but it's for quick turnaround... eat-n-go or takeaway. And bar is a drinking establishment that also sells food, often small plates or bar food.
When would you eat at these places? As often as possible!
Phil over 3 years ago