Empires and Imperialism
In the mid-19th century, some European countries (notably, France, Germany and Austria) were called empires. This word, taken from the Roman Empire, meant a strong central government that ruled over its own territory as well as land it had conquered. This term was applied as well to territories outside the European continent which were subjected to rule by a European power. This latter meaning is what is meant by European "imperialism."
This process began in the 15th century, when Portugal -- in search of trade routes to India -- had established trade colonies along both coasts of the African continent. These colonies became outposts from which were shipped gold, sugar and slaves. In the 16th century, Spain had conquered the two great civilizations of central and southern American and established an empire from which it extracted tremendous amount of silver. Then, in the 17th century, England had established settlement colonies in North America, as refuge for religious minorities (primarily in the north) and as land to be farmed (in the south). These "empires" in the Americas, had, for the most part, become by the later 1800s independent countries.