"It is on its way" is a common expression that means "it's arriving soon." The word "way" can mean "road" or "path," in English, like in the common question for directions: "Do you know the way to ______?" (the beach, main street, the hotel, etc.). So the phrase "It's on its way" is a way of saying "it is on its path to you." It is very common to hear this expression when you are waiting for something: a delivery to your home or office, a meal at a restaurant, a letter or package, etc. You can ask "Is it on its way?" and the other person can reply, "Yes, it's on its way right now." I hope this helps!

the food is on its way - that is to say it is being prepared for you to eat, and will be ready shorty. literally on its way from the kitchen cupboard to your plate.