What do you do when you run out of something you need? As the wheels of industry kept turning in Europe, industrialized nations started running out of raw materials.
They began to use colonies to get the materials they needed. Africa, especially, was rich in resources. European nations competed to build their empires and supply their industries by colonizing Africa.
These colonies not only supplied raw materials, they also provided new customers for European businesses. This practice of acquiring more lands, establishing colonies, and controlling those colonies is called imperialism. The Age of Imperialism would come to define a period of European expansionism that changed the world.