Answer:
Countries along the coast of Africa tend to be wealthier and more developed than countries in the middle of the continent, due to the natural, economic, and logistical advantages that having a coastlines provides for a country, for example, by making it easier for coastal countries to engage in international trade than it is for inland, landlocked countries.
Another difference is that countries along the coast of Africa tend to be more urbanized while countries in the middle of the continent tend to be more rural, precisely because the higher economic activity of the coastal countries fosters urbanization processes.