Norway is a DC because it has timber and crude oil which can be made into furniture and petrol respectively so this can cause it to develop faster than other countries with few or no natural resources/raw materials
Money earned from selling the raw materials can be used to build roads, hospitals, etc and so improve the people’s S/L and Q/L.
You are a businessmen and you sell mobile phones. Would you rather open up your shop in the city (core) area where there are many people who will buy your phones or in the village (periphery) where people are poorer?
This effect where the periphery areas get POORER and POORER because people and raw materials are going to the city is called
The Backwash Effect
But its not all gloom and doom for the periphery areas LAH!
Governments sometimes purposely encourage industries to go to the poorer areas to set up, or governments of poorer countries encourage industries to set up in their countries by offering them benefits like cash, etc
DCs have a higher literacy rate than LDCs, and so with more people being able to read and write, more people will work in secondary and tertiary industries and these are the industries that usually bring in more money for the country (S/L) so it becomes more developed!
Wars and instability have discouraged industries from setting up in countries and tourists from visiting the countries and this has reduced money coming in for these countries, slowing down their development
So, countries which often have wars and are unstable/unsafe stay less developed