T-Lymphocytes, or T-cells, are a type of white blood cell that play a crucial role in the immune system. They originate from stem cells in the bone marrow and mature in the thymus gland. T-cells are essential for identifying and attacking infected or cancerous cells in the body. There are several types of T-cells, including helper T-cells, which assist other immune cells, and cytotoxic T-cells, which directly kill infected or abnormal cells. T-cells recognize specific antigens, which are unique markers on pathogens, allowing them to target and eliminate threats effectively.