All of them, eventually! But if you are trying to get a flavor for each neighborhood, this might help.
Also, there are longer descriptions on each tour page. Click the links below:

Original Greenwich Village: A food tasting journey through the West Village.

The Greenwich village tour winds through a very quaint, picturesque, charming neighborhood in an old Italian section of NYC with some great mom & pop shops. Most food tastings are Italian. And this tour is all about specialty shops – a bread shop, a cheese store, a pork store and an olive oil shop. This is the tour that started Foods of NY Tours.

Chelsea Market & The Highline: A food adventure in two hip industrial areas.

This tour is mostly indoors (2/3 indoors) though the Chelsea Market which is an old industrial building in NYC – a great tour for a cold winter day or hot summer afternoon. The market is filled with food shops and many bakeries where you can see some behind the scenes action. We also visit the highline which is NYC’s newest outdoor elevation park and dip into the trendy meatpacking district.

Heart & Soul of Greenwich Village: Enjoy the Culinary Melting Pot of the Village along with it’s counter culture, and sights.

The Heart & Soul of Greenwich Village food and culture tour introduces you to our favorite neighborhood spots. The tour travels through a cool neighborhood known for the music scene and visits the historic Washington Square Park.

Gourmet Chinatown: Discover Chinatown from Dumplings to Peking Duck.

Tackle a neighborhood that is hard to navigate through – even for New Yorkers. We’ll help you finally discover where to eat in NYC’s large Chinese neighborhood. There is a lot of food on this tour and several indoor sit down tastings – which justifies the higher ticket price on this one.

Nolita & Little Italy’s Secrets: Enjoy cobblestone streets and downtown eats.

Visit the old little Italy and taste from some Italian (as well as American, Mexican and British) restaurants. Learn mafia history. This area is quaint while still being very funky, downtown and cool. Learn some pop culture, see The Godfather and Scorsese film locations. Learn about Graffiti culture and see some interesting examples.

Brooklyn: An exclusive history and gastronomy lesson complete with Brooklyn Bridge views

Follow the trail of NYC’s immigrant groups from their beginnings on the Lower East Side of Manhattan and then cross over the Williamsburg Bridge to see where they’ve settled. Visit the Polish section of Greenpoint and feast on kielbasa sausage and pierogies. Watch our Pizzaiolo prepare a delicious brick-oven pizza and taste chocolates at the famous Jacques Torres Chocolate Shop.