I think the differences between of it is that developed countries refers to the sovereign state, whose economy has highly progressed and possesses great technological infrastructure, as compared to other countries than developing countries which is in process of their growth or is a country which has a slow rate of industrialization and low per capita income.
There are so many inequalities and differences between developed and developing countries in terms of the economy and the way of life of their citizens. You're right if the per capita income of every person in developed countries can reach $3000 every month just for ordinary employees, in developing countries only paid $80 per month, obviously the difference is..