A group is a collection of possible CLI options and arguments.
Essentially it provides the context of a action called via CLI.
For example: When calling something like dummy.exe test --flag
then test is the command context since the action test should be invoked.
Now --flag can now be either created on the Root group or
the test group.
When options are defined on the root group, they are available to every
child group as well, while options defined on a child group are only available to the
child group and its children.