The heavy-duty power bar in a network rack that feeds every device from one controlled source.
Like the main breaker panel for a cabinet of equipment: one tidy, labelled place that decides which device gets power.
A five-person engineering firm's network cabinet had three daisy-chained consumer power bars. A cleaner's vacuum tripped one. The firewall, switch and a NAS went down together, and nobody knew which plug went where.
Network covers the on-premises firewall and switch. A labelled PDU in the cabinet, ideally one that can be switched remotely, makes a remote restart possible instead of a drive across town.
Example scenario: A small accounting firm's firewall froze on a Saturday. The switched PDU let the outlet be turned off and on from a laptop at home. The firewall came back in two minutes, staff working remotely got their VPN back, and nobody drove to the office.
Do I need a PDU or is a power bar fine?
If the equipment is in a cabinet, a PDU keeps it labelled, rated and on the UPS. A switched one earns its cost the first time something needs a remote restart.

Every WILDCARD card exists to solve one named problem. Find yours.