It represents a necessary clause in contracts designed to protect companies from liability in case of a natural or unavoidable disaster, that would prevent participants to complete their share of responsibilities. This clause cold covers everything from the increased awareness of epidemics that may lead to pandemics, asteroids, volcano eruptions, cybernetic warfare, or nuclear disasters.
The three main characteristics which make this clause appliable are unforeseeable circumstances, external factors, and inability to perform.