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 and killer T cells. Helper T cells assist other immune cells in responding to infections, while killer T cells directly destroy infected or cancerous cells. Together, they work to keep the body healthy and protected.