South America is the 4th largest continent, located mostly in the tropics, with coastlines along the Atlantic, Pacific, and Caribbean Seas. It contains three main physical regions - the Andes Mountains, plains, and the lowlands and plateaus of Brazil. The continent was dominated by indigenous civilizations like the Inca prior to European colonization starting in the 15th century. Today, most countries in South America have left-leaning governments, Spanish and Portuguese are the dominant languages, and the economies rely heavily on natural resource extraction and agriculture.