I wrote an article about this 8 months ago.
We have lots of countries falling under the underdeveloped category.
They are countries that vast majority of the population are poor with little industries. This means they do not produce anything or little materials that would have been sold to strengthen their economy.
Taking a line from my post.
*Basically it is believed that when there are lots of industries that manufacture goods for sale, they will definitely employ workers in their numbers, paying them, the workers in turn use this income to pay for goods and services rendered by other members of the society.*
Sudan and Bangladesh are examples of underdeveloped countries.
You can check the post I made to get more details https://steemit.com/life/@zoneboy/developed-developing-underdeveloped-countries-fully-explained