Have you ever cooked something on a stove or in an oven? Well, cooking something slowly, or using a 'slow fire' means that you cook it at a lower temperature for a longer time.
This is like when you make soup or stew with your mommy or daddy. They put everything in a pot and then turn on the heat to a very low setting. This helps the soup or stew to cook slowly and all the yummy flavors to mix together. If they turned on the heat really high, the soup or stew would burn or boil over, and it wouldn't taste very good.
Slow cooking can make meat or vegetables really soft and tender, like when you cook a roast in the oven for a long time. It can also make things taste better because the slow cooking process brings out all the delicious flavors.
So, remember, when you want to cook something slowly, use a low heat and wait patiently until it's ready. It might take longer, but the end result will be worth it!