Imperialism has a longer history than Colonialism. While the history of colonialism dates back to 15th century, Imperialism has its origins dating back to the Romans.
Colonialism and imperialism are often used interchangeably, but they are two different words having different meaning. As both colonialism and Imperialism means political and economic domination of the other, scholars often find it hard to differentiate the two.
Colonialism is termed as building and maintaining colonies in one territory by people from another territory. It can altogether alter the social structure, physical structure and economics of a region. It is quite normal that in the long run, the traits of the conqueror are inherited by the conquered.
For example: British ruling the American colonist Spain ruling over the Aztec (Mexico)
Colonialism is a term used to describe the settlement of places like India, Australia, North America, Algeria, New Zealand and Brazil, which were all controlled by the Europeans. It is the movement of people to the new territory and living as permanent settlers. Though they lead the life as permanent settlers, they still maintain allegiance to their mother country.
Imperialism means creating an empire, expanding into the neighboring regions and expanding its dominance far through sovereignty or indirect mechanisms of control. It is described where a foreign government governs a territory without significant settlement. The scramble for Africa in the late 19th century and the American domination of Puerto Rico and the Philippines can be cited as examples of Imperialism.