Device management covers everything that happens to a device after it is built: provisioning with credentials, configuration, health monitoring, firmware updates and decommissioning. For a handful of devices this can be manual; for thousands it has to be automated, which is why most IoT platforms include it and standards such as LwM2M exist to describe it.
The value shows when something goes wrong. A fleet where you can see which units are offline, roll a firmware fix to a test group and then to everyone, and revoke a compromised certificate is far cheaper to run than one that requires a site visit. See Device management and OTA updates.
Part of the IoT Glossary. Spotted an error or a missing term? Tell us.