Tomato sauce is a product made by cooking fresh tomatoes down into a medium-thick sauce then straining out seeds and peels. The product is available natural or seasoned. Tomato sauce is used as a base or an addition to many sauces and soups. It is less concentrated than tomato paste and thinner than tomato puree.
Ripe tomatoes made into sauce are naturally sweet so make sure to look for a brand that does not add sugar. For example, Hunts brand does not add sugar, almost all other brands do.