Peyer's Patches are small clusters of lymphoid tissue found in the lining of the small intestine, particularly in the ileum. They play a crucial role in the immune system by monitoring intestinal bacteria and preventing the growth of pathogenic bacteria in the intestines. These patches contain specialized cells that help in the production of antibodies, which are essential for fighting infections. Peyer's Patches are part of the gut-associated lymphoid tissue (GALT) and contribute to the overall immune response by facilitating the interaction between the immune system and the gut microbiome.