The HP 490371-001 AC power cord connects a compatible power adapter to an AC outlet. HP lists this specific part for use in North America, making it a region-specific cord for powering equipment through an adapter.
It is a black, 3-pin cable measuring 1.83 m. Its length gives some flexibility in placing equipment near an outlet. The equipment-side connector is a female IEC 320 EN 60320 C5 type.
This is a power cord, not an AC adapter; it connects the adapter to mains power.