Traditional Italian sauces are used to add moisture, flavor and look great on many Italian dishes. Most of the popular sauces are meant to go on pasta. You'll find that there are so many of them because they all come from different parts of Italy. Most of these sauces are red and many of them have a garlic and olive oil base. The tomato sauce varieties of sauce include Pasta Puttanesca sauce that has anchovies, capers, chili peppers, black olives and garlic and Bolognese sauce that has ground or minced meat that often only has a small amount of tomato. More recently, creamy sauces are gaining in popularity. For instance, Alfredo sauce isn't really Italian, but something that was developed by Italian Americans. Some of the more popular northern Italian sauces include Bolognese sauce that contains boiled meat.
Marinara, or mariner's sauce is a red sauce that is actually Italian American. It is made with onion, herbs that include basil, garlic and tomatoes. There are many different recipes for this kind of sauce and some of them include capers and olives, as well as other spices.
The traditional Italian cooking that you'll find in the United States uses Marinara sauce as a way to flavor everything from pasta to pizza and even is used to compliment rice and seafood. Italians from Italy make reference to marinara as we know it only when using other, non Italian recipes and they most often only use it when flavoring a seafood dish. An example would be spaghetti alla marinara, which literally means "mariner's spaghetti". This is a dish that might include some kind of seafood or shellfish and might not have any kind of tomatoes.
Pesto comes from Genoa, which is in the Liguria region of Northern Italy. Pesto all a Genovese is one popular pesto dish from this area. Pesto comes from the word "pest", which literally means "to pound". This term is referring to the crushed garlic and herbs that are in the sauce. Pesto all Genovese contains salt, garlic, Genovese basil and Ligurian extra virgin olive oil, as well as European pine nuts and a hard cheese that is grated such as Parmigiano Reggiano.
Pesto is most often added to pasta, and tradition has it being served with Mandilli de Sa. The traditional recipe has boiled potatoes and small green beans in it as well. They are often boiled in the same pot as the pasta. Pesto has been known to be added to minestrone, and it is occasionally served on a meal consisting of sliced boiled potatoes, tomatoes and beef.
Bolognese sauce is a type of meat sauce for pasta that comes originally from Bologna, Italy. Bolognese sauce is occasionally mistaken for a tomato sauce, however authentic Italian recipes only have a little bit of tomato concentrate in them. Traditional recipes have the ingredients of pancetta, onions, beef, carrots, tomato paste, meat broth, celery, white wine and cream or milk. Different recipes that all come from Bologna will use other ingredients such as chopped pork or pork sausage, white chicken, goose liver or rabbit in addition to the beef on a special occasion. The residents of Bologna most often serve their popular ragu with tagliatelle that is freshly made and the famous green lasagna.
Neapolitan sauce is a name that has been given to many different sauces that have a tomato base and come from Italian cuisine, these are most often put over pasta and have Parmesan cheese sprinkled on the tip. Many of the recipes for these sauces have garlic and onions in them. Other ingredients might include bay leaf, thyme, basil, oregano, cloves, peppercorns and even mushrooms.
This kind of sauce is extremely popular in Southern Italy because there was a time where there wasn't much meat available.
Ragu is a term in Italian that essentially means meat based sauce that is most often served over pasta. A traditional Italian ragu might be something like ragu alla Bolognese (Bolognese sauce), ragu alla Napoletana, or Ragu alla Barese. This type of sauce is most often made by making a soffritto, or mixture of celery, chopped onions, seasonings and carrots that have been part fried and then adding the meat. Then other ingredients, including some tomatoes are added and the mixture is simmered for many hours.
Fra Diavolo, which is Italian for "Brother Devil". This is the name for the spicy sauce that often covers seafood or pasta. Most of the versions of this sauce have a tomato base and chili peppers make it spicy, but it's also used to refer to sauces that don't use any tomatoes and use cayenne or other peppers for seasonings. Chef Mario Batali says that this sauce is actually almost never served in Italy and has been created by Italian Americans.
Vodka sauce is a red sauce that consists of smooth tomato sauce, traditional Italian herbs, vodka and cream. It became very popular in the 1970's when one version actually won the national recipe competition that is held in Italy. This is an essential ingredient to penne alla vodka, but it might have been around long since it is said to have been "invented" in the 70's. While traditional Italian cooking does commonly use alcohol, it is more often wine than vodka.