Food
Food is needed to fill your hunger in the game. You can find wild berries, tomatoes, and even pumpkins. If you obtain a fishing rod, you can fish, and then cook it with a fire to eat it.
Campsite Garden
In your campsite, you can plant seeds from various plants to grow more food. That way, you don't have to go in the wild, and risk your life. All though, you have to have the plant not fully grown yet, and use a trowel to get a seed from it. It will grow back eventually in the wild. After it has fully grown, you can pick it.
You can water your plants with the watering can. It makes them grow a little faster and earns you XP.
WARNING: Once you've picked it in your garden, you must obtain a new seed from the wild to grow it again.
Extras
Berries give: 12% Food, 2% Health
Tomatoes give: 50% Food, 4% Health
Raw fish cannot be eaten.
Cooked Fish give: 90% Food, 15% Health
It is best to save pumpkins for medicine.