Salsa is the Italian and Spanish term for sauce, and in English-speaking countries usually refers to the sauces typical of Mexican cuisine known as salsa picante, particularly those used as dips.

Salsa is often a tomato based sauce or dip which is heterogeneous and includes additional components such as (but not limited to) onions, peppers, beans, corn, and various spices. They are typically piquant, ranging from mild to extremely hot.

Most jarred, canned, and bottled salsa and picante sauces sold in the United States in grocery stores are forms of salsa cruda or pico de gallo, and typically have a semi-liquid texture. To increase their shelf lives, these salsas have been cooked to a temperature of 175 °F (79 °C). Some have added vinegar, and some use pickled peppers instead of fresh ones. Tomatoes are strongly acidic by nature, which, along with the heat processing, is enough to stabilize the product for grocery distribution.

Picante sauce of the American type is often thinner in consistency than what is labelled as “salsa”. Picante is a Spanish adjective meaning “piquant”, which derives from picar (“to sting”), referring to the feeling caused by salsas on one’s tongue.

Many grocery stores in the United States and Canada also sell “fresh” refrigerated salsa, usually in plastic containers. Fresh salsa is usually more expensive and has a shorter shelf life than canned or jarred salsa. It may or may not contain vinegar.

Taco sauce is a condiment sold in American grocery stores and fast food Tex-Mex outlets. Taco sauce is similar to its Mexican counterpart in that it is smoothly blended, having the consistency of thin ketchup. It is made from tomato paste instead of whole tomatoes and lacks the seeds and chunks of vegetables found in picante sauce.

While some salsa fans do not consider jarred products to be real salsa cruda, their widespread availability and long shelf life have been credited with much of salsa’s enormous popularity in states outside of the southwest, especially in areas where salsa is not a traditional part of the cuisine. In 1992, the dollar total of salsa sales in the United States exceeded those of tomato ketchup.

From Wikipedia.