On the label, you can read what is in the food. You can check whether there are shrimp in your shrimp salad or if your eating real bacon in your bacon Tart.
The prepared food is usually made out many different ingredients some you would want to have in your diet and others that you may not want to be eating. Ingredients are the different things you put in the food. In shrimp salad ingredients are, among other things, shrimp and mayonnaise... but some food manufacturers may add artificial flavorings to enhance flavor and preservatives into the food to increase shelf life.
But food manufactures must abide by the law so they must state on the label exactly:
Who is responsible for the item.
The item's actual name eg. wheat buns and not only the sales name such as. Teddy bear buns.
The method of treatment IE. how food is processed. is the fx. "smoked" or "baked".
Composition IE. what ingredients and how many.
Weight exclusive packaging, it is called the net weight.
Date labeling should be on almost all items and if it deteriorates quickly it should have a "use-by date."
Storage if the item should be stored in a certain way in order not to be bad eg. "Refrigerate after opening".
Instructions for use, if it is necessary in order that the food will be made in a healthy way eg. It should read that some beans must be soaked in water and boil for a long time.