Coconut milk is an ingredient that is frequently called for in Thai and other Southeast Asian cooking, and also frequently pops up in recipes for baked goods, particularly in recipes that are showcasing coconut in some form. You might think that coconut milk is simply the liquid inside of a coconut, but it is actually made by making a puree of equal parts water and fresh coconut meat, cooking it until hot, then straining it to remove as much of the solid material as possible. This yields a creamy liquid with a consistency similar to milk that has a nice coconut flavor. Coconut milk is unsweetened, so its flavor often seems very mild until it is added to a pie , a sauce or some other dish. A second straining of the coconut used to make coconut milk will yield a lower fat and slightly less rich version of coconut milk, usually sold as light coconut milk.
Coconut milk is great for imparting richness into ice creams and custards, both when you are trying for a nondairy recipe (many vegan recipes call for coconut milk) or you are making a coconut-flavored dessert. Lower fat coconut milk will work in just the same way, but much like regular low fat milk, it isn’t as rich and there are some recipes where you’ll notice a slight difference in the texture of the finished product – such as ice creams. For quick breads and cakes that might call for coconut milk, both regular and light usually work beautifully and you really won’t notice a difference between the two (this is when I’ll opt for light coconut milk, personally). On the savory side, both will work in soups and sauces, but pay attention to the original recipes as some will call for one or the other and you might get a slightly better result when you opt for regular coconut milk over light.