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. They did this by colonizing Africa.
These colonies supplied raw materials. They also provided new customers for European businesses. The practice was to acquire more lands, establish colonies, and control those colonies. This is called imperialism. The Age of Imperialism describes a period of European expansionism that changed the world.