The formula: when this is, that is; from the arising of this, that arises; when this is not, that is not; from the ceasing of this, that ceases.
Nothing arises in isolation. Every phenomenon depends on conditions; remove the conditions and the phenomenon does not occur. This is the logical and experiential base of Emptiness: nothing has self-standing existence, because everything is held in a web of dependencies.
The twelve-link chain (nidanas) — ignorance → formations → consciousness → name-and- form → the six sense bases → contact → feeling → craving → clinging → becoming → birth → aging-and-death — maps the cycle of Samsara and shows where it can be interrupted.
Nagarjuna made dependent origination the hinge of Madhyamaka philosophy: emptiness is dependent origination, seen clearly.