Memory T cells are a type of immune cell that play a crucial role in the body's defense against infections. After the body encounters a pathogen, such as a virus or bacteria, some T cells become memory T cells. These cells remain in the body long after the infection has cleared, allowing for a quicker and more effective response if the same pathogen is encountered again. When the body is re-exposed to the same pathogen, memory T cells can rapidly recognize and attack it. This ability to remember past infections helps the immune system respond more efficiently, often preventing illness or reducing its severity.