The central concept of TENET revolves around time inversion, where objects and people can reverse their entropy, allowing them to move backward through time.

 

The Algorithm is a device that, if fully activated, can invert the entropy of the entire world, essentially reversing time on a global scale, leading to catastrophic consequences.

 

Time inversion works by reversing the entropy of objects or individuals, allowing them to move backward through time while the rest of the world moves forward. This concept drives many of the films action sequences and plot points.