A foodstuff is any substance that people use as food. The word treats food as a material or commodity rather than as a specific meal or dish. When a grocery store manager talks about ordering foodstuffs, she means the raw ingredients and packaged items that fill the shelves: flour, rice, canned vegetables, dried beans, and so on.

The word appears most often in contexts involving trade, storage, or large quantities. A ship's captain might inventory the foodstuffs in the cargo hold before a long voyage. A humanitarian organization delivers emergency foodstuffs to areas affected by natural disasters. Historians studying ancient civilizations examine what foodstuffs people grew and traded.

While you'd say “I'm hungry, let's get some food,” you probably wouldn't say “let's get some foodstuffs.” The word sounds formal and somewhat technical, like you're discussing food as a category or resource rather than something delicious you're about to eat. A chef plans a menu with specific dishes, but a warehouse stores foodstuffs.