T-cells are a type of white blood cell that play a crucial role in the immune system. They help the body fight off infections and diseases by recognizing and attacking harmful invaders, such as viruses and bacteria. T-cells are produced in the bone marrow and mature in the thymus, which is where they get their name. There are different types of T-cells, including helper T-cells that assist other immune cells and killer T-cells that directly destroy infected cells. By working together, T-cells help maintain the body's defense against illnesses, making them essential for overall health and well-being.