Condensed milk and evaporated milk are often confused because their names sound so similar. After all, doesn't evaporation condense/concentrate what it leaves behind? Actually, yes. Unsweetened condensed milk and evaporated milk are the same thing. To make it, 60% of the water in the milk is removed by evaporation in a high-heat environment. The heat causes some of the natural sugars in the milk to caramelize, so it is often slightly darker in color than plain milk. While the original evaporated milk was made from whole milk, it also comes in nonfat and low fat varieties. It is sometimes used in baking, but is most often suggested as a lighter version of cream for soups and coffee drinks. It is shelf-stable, so it's a great thing to keep around the house in case a recipe calls for it.

The difference between condensed and evaporated comes in to play when you have sweetened condensed milk, which cannot be substituted for evaporated milk. Sweetened condensed milk contains a very large amount of sugar. In fact, at least 40% of what is inside a can of sweetened condensed milk is sugar. It is therefore very sweet, in addition to being shelf-stable.  Sweetened condensed milk, in addition to being used in baking and candy-making, is a popular addition to drinks like Vietnamese coffee and Thai iced tea. Its most popular use at the moment is for making dulce de leche, which is a heavily caramelized version of sweetened condensed milk. Again, it is shelf stable, so rather than wondering about substitutes, it is best to pick up a can and stick it in the back of the cupboard in case it is needed.