Habitat refers to the natural environment where an organism lives and provides everything it needs to survive, including food, shelter, and mates. There are three main types of habitat: freshwater, marine, and coastal. Freshwater habitats include rivers, lakes, and streams, while marine habitats are the oceans and seas. Coastal habitats are where land and sea meet. Major habitats include forests, grasslands, deserts, mountains, polar regions, and aquatic habitats. Habitat can be affected by both natural changes like fires or drought as well as human-caused changes like habitat loss.