When Europe started the Industrial Revolution there was an increased demand for materials such as steel, gold, and others. This sparked the interest in Africa by European powers. Who had more money from the Industrial Revolution had more power and this was very important.
European powers wanted access to African resources, to avoid wars the Berlin Conference of 1885 was established and the African Continent was divided between European Powers.
People in Africa were forced to grow cash crops like rubber, cotton, peanuts, palm oil, cocoa, and sisal so they could feed Industrial needs in Europe.
Britain, for example, wanted the South Africa region because it was a useful stop for their ships which went to India - another British colony -. Also, the Suez Canal in Egypt served as a route to the oilfields in the Middle East.