CLI stands for Command Line Interface. This is a set of little scripts that let you talk with MiGA through the terminal shell. If MiGA is in your PATH (see installation details), you can simply run
miga in your terminal, and the help messages will take it from there. All the MiGA CLI calls look like:
miga task [options]
task is one of the supported tasks and
[options] is a set of dash-flag options supported by each task.
-h is always there to provide help.
If you're a MiGA administrator, this is probably the most convenient option for you.