What is the role of self interest in a market economy?

self-interest means people act to better their life. they do this by becoming entrepreneur, getting jobs, buying things, and all of these things help the economy. entrepreneurs turn materials and money products and services, creating jobs and said products and services. people who get a job work to create products in services. then comes competition. in the free market, only the best get ahead, so companies try to make themselves more profitable by increasing efficiency, coming up with new ideas, etc. by doing this, more products and services are created per person, and therefor each person can have more products. basically, they create insentive for people to make more stuff, and therefor people can have more stuff.