The strips run both vertically and horizontally at regular intervals known as power mesh.
It is a metal layer that carries the power.
IR drop is the voltage drop in the metal layer. The VDD and VSS supply is uniformly distributed in the chip through a metal layer across the design, and each of the metal layers have their finite amount of resistance.
When we apply the voltage, the current starts flowing through these metal layers and a part of the applied voltage is dropped due to the resistance of a metal wire and current. This drop is called IR drop. IR drop causes the delay of cells, causing setup and hold violation.
When the high current density is flowing through the metal layer, the electrons in the metal layers are displaced and atoms get displaced from their original position, causing open and shorts in the metal layer.