How Chicken's Digest Their Food
Chickens consume food with their beaks and pass it into a large sack called the crop. The crop is really just a storage bag and allows the chicken to eat large quantities of food quickly so they are not exposed to predators for long periods while they are eating.
The food is then sent to the proventriculus where it mixes with enzymes that begin the digestive process. However, the food particles may be too large for the chicken to effectively digest and so the food and enzymes travel next to the gizzard for further processing.