Cytotoxic T cells and helper T cells are two distinct types of T lymphocytes. 

Cytotoxic T-cells, also known as CD8+ T cells are capable of directly targeting and eliminating infected or malignant cells to prevent further spread of the infection or malignancy. 

Helper T cells, also known as CD4+ T cells play a supportive but pivotal role in coordinating the immune response. When helper T-cells sense an infection, they release cytokines, which are molecules that send messages to other immune cells. These cytokines help activate cytotoxic T-cells to fight the infection. Helper T cells also maximize the cytotoxic T cell population expansion during a primary immune response, ensuring a swifter, more efficient immune response.