Islands are pieces of land that are completely surrounded by water. They can be found in oceans, seas, rivers, and lakes. Some islands are large, like Greenland, while others are small, like Bikini Atoll. Islands can be formed in various ways, such as volcanic activity or the rising and falling of sea levels. Many islands are home to unique plants and animals that are not found anywhere else. For example, the Galápagos Islands are famous for their diverse wildlife, which played a key role in Charles Darwin's theory of evolution. People often visit islands for their beautiful beaches and natural beauty.