Industry is the production of goods and services, which make an economy run. The basics of an economy require certain components that are used to feed and house the citizens. Agriculture feeds and clothes the people, while mining and timber industries are used for housing and infrastructure.
Once the plants have been harvested, and the metals mined they must be refined before use. Although most food that is grown can be immediately used, a large society needs to be able to store the food for later consumption. Buildings can store grain and cans will keep vegetables fresh for many months.
After refining the raw materials, the refined materials can be used to make something. Wood, concrete, and metal are used in the construction of buildings to house large numbers of people. Every object that is not used immediately after gathering goes through the gathering, refining, and finally manufacturing process before use.
A stable economy that can meet its own needs is (hopefully) healthy enough to begin to offer less basic services to the community. Healthcare, education, law, and leisure activities are examples of a more advanced economy, that can offer its people more than the basics needed to survive.
An economy that produces an excess of goods and services can offer these in trade with other areas that cannot, for some reason, meet the needs of their own population. An infrastructure is needed to get these goods and services from the place that has them to the place that needs them.
The building of roadways, railroads, and a shipping system helps the local economies expand, but also enables the population to travel from place to place with less difficulty.
All economies are dependant upon the four basic areas of industies. When one industry suffers it affects all the others. Industries create wealth, stability, and security for the population.