The terms, green beans and string beans, are synonyms for the same produce item!  When someone says, "Green beans they are usually referring to the most common variety, is called Blue Lake Green Beans. Blue Lakes are the classic green bean and are also referred to as string beans. There is a type of green bean called Haricot vert, which is also known as French beans. These beans are a thinner, shorter and shorter than Blue Lake beans, which means they are more tender and take less time to cook. French beans are commonly sold frozen.