The Node Group Data report displays the list of nodes that belong to each group, the user groups that have access to each node group, and, if applicable, the rules that define the node group. The list of nodes is in the report details, which you can view by double-clicking a row in the report page, or save to a CSV file. See Save a Report to a File.
The Node Asset report displays the list of groups each node is a member of. See Node Asset Report.