Most vSphere admins are more than comfortable with using Update Manager to download patches and update their environment, but few that I talk to actually know a huge amount about the Update Mangaer Download Service (UMDS). UMDS is tool you can install to download patches (and third party VIBs - I’ll get to that) for Update Manager and it’s useful for environments that don’t have access to the internet, or air-gapped, and also for environments with multiple vCenter Servers where you don’t necessarily want to download the same patch on every server.