Phage display is a laboratory technique used to study interactions between proteins, peptides, and other molecules. It involves attaching a specific protein or peptide to the surface of a bacteriophage, a virus that infects bacteria. By displaying a variety of proteins on the phage, researchers can screen for those that bind to a target molecule, such as a receptor or antibody. This method allows scientists to identify and isolate proteins with desired properties, making it valuable in fields like drug discovery and vaccine development. Phage display has led to the development of therapeutic antibodies and improved understanding of protein interactions.