In order to push a manifest, its classes, and assets to systems, they need to be known by Puppet Master. Grouping is practical if you want to push a manifest to a number of hosts without having to modify each configuration node.
In contrast to what the title wants you to believe, you cannot create a group and add nodes. However, you can group nodes and make them behave in a similar way to groups.
Nodes and node groups are defined in /etc/puppet/manifests/site.pp
or a file at /etc/puppet/manifests/site.pp
.