Full fat coconut milk is thick and found in a tin. It is usually used in desserts and rich sauces, especially in Indian cuisine. The top of the tin often contains a layer of coconut cream that can be seperated to use as vegan whipped cream.
Reduced fat coconut milk or light coconut milk is the lower fat version of full fat coconut milk and is also found in a tin. Often in the Asian section of supermarkets.
It is made by the coconut flesh being grated and soaked in hot water. The cream floats to the surface, and it is squeeze to retrieve the coconut milk.
However, coconut milk is also a dairy-free milk alternative. It can be purchased in cartons from most supermarkets. This type of coconut milk is thinner and has less fat content.