This refers to: Replacing one release with another without upgrading the feature set. Update to fix a bug or to replace a release that is no longer supported.
This refers to: Replacing a release with one that has an upgraded feature set. Upgrade to add new features or technologies, or replace a release that is no longer supported. Upgrades are not free of charge.
Cisco IOS Auto-Upgrade Manager automates the process of updating or upgrading Cisco IOS Software versions on Cisco 1800, 2800, and 3800 Series Integrated Services Routers directly from the console with Cisco IOS 12.4(15)T or later versions.