The Age of Discovery, or the Age of Exploration (approximately from the beginning of the 15th century until the middle of the 17th century), is an informal and loosely defined term for the period in European history in which extensive overseas exploration emerged as a powerful factor in European culture and which was the beginning of globalization. It also marks the rise of the period of widespread adoption in Europe of colonialism and mercantilism as national policies. Many lands previously unknown to Europeans were discovered by them during this period, though most were already inhabited. From the perspective of many non-Europeans, the Age of Discovery marked the arrival of invaders from previously unknown continents.