Chicken wing tips are often discarded or used for stock.
The tip is the smallest and least meaty section of a chicken wing. It contains skin, connective tissue, and bones but comparatively little meat, so cooks often separate it from the drumette and flat before preparing wings. Rather than throwing it away, many use it to enrich chicken stock.
Stock is made by simmering bones and connective tissue in water, often with vegetables such as onion, carrot, and celery. Collagen from connective tissue breaks down into gelatin, giving a well-made stock body and a fuller mouthfeel. Wing tips are useful because their bones and cartilage release flavor and gelatin during a long simmer.
This is different from gravy, which is usually a finished sauce made from meat juices, stock, thickener, or other ingredients. Marinade and brine are also preparation liquids, but they season or tenderize food before cooking rather than forming the base of a soup or sauce. Some cooks freeze wing tips and accumulate them until there are enough for a batch of stock.