A T-Cell Receptor (TCR) is a protein found on the surface of T-cells, which are a type of white blood cell crucial for the immune system. TCRs recognize and bind to specific fragments of proteins, known as antigens, that are presented by other cells. This interaction helps T-cells identify and respond to infected or cancerous cells. Each TCR is unique, allowing the immune system to target a wide variety of pathogens. When a TCR binds to its specific antigen, it triggers the T-cell to activate and proliferate, leading to an immune response that helps eliminate the threat.