There are two main ways to talk about food in Chinese:
饭 (fan4): usually used when talking about a meal, or something that you are ready to eat. It also means “rice”, since rice is a staple of a Chinese food diet.
食物 (shi2 wu4): refers to food in general, often before it is cooked and prepared. If you buy food from the grocery store, you would typically say shi2 wu4 rather than fan4.