Culinary terms are plentiful and can be confusing. Personally, when reading a recipe I used to assume I knew what was meant when a recipe asked me to sweat or sauté onions, but I really didn’t.
So what is the difference between sweating and sautéing? It’s simple. In fact it is held in just one word: browning.
When you are sautéing food you do it over medium to high heat and you want the food to brown and caramelize. By agitating the pan regularly you help the food to brown evenly. Generally this is done to help build a rich flavour profile which includes that lovely caramelized taste.
Sweating on the other hand should not brown food. Instead the food is cooked over low to medium heat and should sizzle very gently so that the food (usually vegetables) can release it’s liquid and flavours into the pan without colouring. If you are making a soup for example sweating the main ingredients can help them to release their more subtle flavours into the soup before the liquid is added. A little trick, if you see your pan is too hot and food is starting to colour, add a tablespoon of cold water, it will cool down the pan quickly and evaporate.
Do keep in mind that people use these terms incorrectly, you may see recipes that say things like “brown the onions by sweating them in butter”. This may be wrong, but it doesn’t matter, as long as you can understand what the recipe wants you to do – you can create great food!