Food is a resource in They Are Billions.
You need food to feed your colonists and army units. You can produce food by building hunter and fisherman cottages or farms. Those buildings produce a variable amount of food depending on where they are placed. Every colonist will consume one food unit. Also, some soldiers need extra food units. You cannot build houses or train soldiers if you don't have the available food required. Food can be produced by some buildings like the Hunter cottage, the Fisherman cottage, Farms...
In the same way as the resources buildings, they have a production radius that will determine how much food they will produce depending on the surrounding environment. The Hunter Cottage prefer woods and fields to find food. The Fisherman Cottage needs sea/rivers. Farms prefer grassy fields.