Christine Giordano There are some sauces and seasonings you can slip into food without anyone noticing—but fish sauce is not one of 'em. The savory sauce has a distinct umami flavor—and it's next-level delicious. Chances are, you've tasted fish sauce at some point, you might be a little fuzzy on what, exactly, it is. So, in case you're wondering, uh, what is fish sauce, really?—yes, it is totally made of fish. The delightfully salty condiment is “very important to Southeast Asian cuisines in particular,” says Andrea Nguyen, cooking teacher and author of The Pho Cookbook, who says that Thai, Vietnamese, and Filipino cuisines incorporate it the most heavily.