The PDB is the electrical backbone. Battery power comes in once and is split into individually fused, individually switched rails — so a fault in one node cannot pull down the whole vehicle.
The autonomy stack can shed load by switching rails off, which matters when energy is the budget that ends the mission.
For engineers
Each rail carries hall-effect current sensing reported on the CAN bus. The software watchdog can trip a rail on overcurrent in firmware, below the level of the host computer, so a hung process cannot melt a harness.