Things that restrict competition, such as government protected monopoly like copyright or patents, or licensing such as certificates of need for hospitals or even the residency process to become a doctor (in the US), or land with advantageous properties that other land cannot replication (i.e. location).

Or simply doing something that requires so much expertise that it requires tens of billions of dollars and decades for others to catch up, such as what TSMC/ASML/Apple/etc.