A peninsula is a geographical feature characterized by land that is surrounded by water on three sides, protruding into an ocean, sea, or large lake. It typically connects to the mainland via an isthmus. This landform can vary in size, from small to large areas, and is often rich in biodiversity and unique ecosystems due to its proximity to water. Peninsulas can also influence climate and serve as crucial locations for human settlement and development due to their access to maritime resources.