Volume eating means choosing foods that are very filling but low in calories. You eat a huge plate of food, feel completely full, and still stay within your calorie target.
The key idea is calorie density. Some foods pack a lot of calories into a small amount. Other foods have very few calories but take up a lot of space in your stomach. Volume eating focuses on the second group.
You still track calories. The difference is that every calorie you eat comes with a lot of food weight behind it.