Baselines contain a collection of one or more patches, extensions, service packs, bug fixes, or upgrades, and can be classified as patch, extension, or upgrade baselines. Baseline groups are assembled from existing baselines.

Host baseline groups can contain a single upgrade baseline, as well as a number of patch and extension baselines.

Virtual machine and virtual appliance baseline groups can contain up to three upgrade baselines: one VMware Tools upgrade baseline, one virtual machine hardware upgrade baseline, and one virtual appliance upgrade baseline.

When you scan hosts, virtual machines, and virtual appliances, you evaluate them against baselines and baseline groups to determine their level of compliance.

Update Manager includes two predefined patch baselines and three predefined upgrade baselines. You cannot edit or delete the three predefined virtual machine and virtual appliance upgrade baselines. You can use the predefined baselines, or create patch, extension, and upgrade baselines that meet your criteria. Baselines you create, as well as predefined baselines, can be combined in baseline groups. For more information about creating and managing baselines and baseline groups, see Working with Baselines and Baseline Groups.