Fat loss- what's the difference between being in ketosis and (simply being on calorie deficit?) why is ketosis said to be better at fat loss.

What is ketosis : Ketosis is the process by which your body process the stored fat to create ketone bodies. this is done to replace sugar as the source of energy in certain organs. The only way to stimulate ketosis is by having low insulin levels in your blood and the way to achieve this is by not eating carbs. If you eat a low calorie diet but it has carbs you're not your body is not going to burn fat into ketone