Groups
A group is a collection of things (members) which can be controlled as a single thing.
Groups are always owned by a technology. Members of a group must be associated with that group's technology.
The state section of a group is special in that any operation performed on it will be applied to the state section of all of the group's members.
By comparison, the configuration and metadata sections belong to the group itself. Thus, it is not possible to change a configuration or metadata property across the members of a group in a single operation like you can with state properties.
The behavior of reading state properties on a group is currently undefined by the SOM and thus the behavior is technology-specific. This may change at some point.