I've been cooking Korean dishes for a few years now but still have some confusion about the different soy sauces used. Some recipes call for soy sauce for "soup" while others do not specify a type. Also, some recipes say that fish sauce can be a substitute for the soup soy sauce. So my question is are the different types of soy sauce interchangeable with each other and/or fish sauce, and what makes this soy sauce for soup different? Are there different types of soy sauce like this used in other cuisines as well? Thanks!