My 'vi' editor skills are rusty so I thought I would use Nano on my Linux 2 Ec2 instance. The legend at the bottom surely helps, but I can not figure out what the 'M-" means. Such as 'M-Undo', 'M-E Redo' and 'M-A Mark Text'. I now realize that the 'alt' key can be used but what is the 'M' trying to tell me? Thanks!
The nano docs explains what M- is:
Meta-key sequences are notated with 'M-' and can be entered using either the Alt, Cmd, or Esc key, depending on your keyboard setup.
M- just denotes activation key, which can be Alt, Cmd, or Esc.