What is one of the primary components of a sandwich?

A sandwich is fundamentally defined by its filling, which is the primary component that defines its flavor and substance. The filling can consist of a variety of ingredients such as meats, cheeses, vegetables, or spreads, and it is what transforms two pieces of bread into a satisfying meal or snack. The choice of filling can significantly influence the overall taste, texture, and appeal of the sandwich.

While garnish, sauce, and seasoning can enhance the flavor or presentation of a sandwich, they are not essential for the sandwich's identity. The filling is essential as it provides the main component that interacts with the bread, thereby making it a sandwich.