Foods are items that refill your hunger bar, and add a layer of saturation to it. The hunger bar is the line of "drumsticks" above your in-game hotbar to the right next to your health. Hunger play an important role in gameplay, and needs to be maintained to keep someone alive, and large amount of food is required to advance through the mod easily, unless difficulty is set to peaceful, in which the hunger bar will not deplete. Saturation is capped based on hunger, which mean if your hunger is near full, then eating a food with low hunger/high saturation is most effective.
If your hunger is at least 9 bars, then your health will regenerate 0.5 hearts every 4 seconds. The player will lose their ability to sprint if their hunger bar is down to 3 bars or lower and if the hunger bar is reduced to 0 (no drumstick are colored in), you will start losing health at the rate of 0.5 hearts, lowering one health to 5 hearts in Easy Difficulty, 0.5 hearts in Normal and killing the player in Hard.
To eat, simply select a food item in your hotbar and hold your right mouse button when your hunger bar is depleted while not facing any entity or blocks with right click feature such as chest, furnace or a villager. However, golden apple can be eaten without the need for a depleted hunger bar.