A peptide is a short chain of amino acids (typically 2 to 50) linked by chemical bonds (called peptide bonds). A longer chain of linked amino acids (51 or more) is a polypeptide. The proteins manufactured inside cells are made from one or more polypeptides.
Peptide. I can still remember very vividly in middle school when I first learned about proteins. My science teacher used Lego building blocks as an analogy to describe them. Each individual brick is like an amino acid, and a few of them locked together to form a peptide. A much longer chain of them is a polypeptide, and then those get assembled together in various complex shapes to form proteins. I'm not sure if it was the most accurate representation of peptide structures that exists, but it did give me a good way to visualize the structure of proteins.
NHGRI Bioethics Core