These are two different recipes, but the ingredients are very similar. Salsa verde is usually based in roasted veggies--like tomatillos, chiles, and jalapenos--and then blended. It's fresher than enchilada sauce and tends to have a bit more texture. A green chile enchilada sauce can have the same ingredients as salsa verde, but in some recipes, it is simmered to reduce the liquid and thicken the sauce. Often, a form of dairy or cornstarch is added for thickening and to make the sauce more creamy. Enchilada sauce also tends to be pureed a lot smoother than a salsa verde.