A bond formed by Dehydration synthesis between a Carboxylic acid group, and an Amine group. These are the basis of polypeptides, such as Proteins

The nature of the chemical bonding within a peptide accounts for the bond’s planarity. The bond resonates between a single bond and a double bond. Because of this double-bond character, rotation about this bond is prevented

There are two possible conformations, the cis and trans conformations, but, for Amino acid, due to to Steric hindrance, the trans is by far the most common. for X-Pro bonds, both have steric hindrance and so both kinds appear.