Your body makes peptides. They're strings of amino acids, which are the "building blocks" of proteins. But a peptide doesn't have as many amino acids as a protein does.
Lab-made peptides can mimic some of those found in your body.
Some of them are used in medications for conditions ranging from diabetes to multiple sclerosis. Studies have also found that certain types may have benefits for your skin, muscles, and maybe your weight. So companies are putting them into skin products and dietary supplements you can buy over the counter.