The idea that firms and resource suppliers in seeking to further their own self-interests in a competitive market economy also simultaneously promotes the public or social interest is a description of:

The idea that firms and resource suppliers in seeking to further their own self-interests in a competitive market economy also simultaneously promotes the public or social interest is a description of the invisible hand. The term invisible hand was used by Adam Smith a Scottish philosopher and economist in the 18th-century. The invisible hand refers to the unintended social benefits that came from an individuals self-interest actions.

That is known as the "invisible hand"