That’s the list of ports that are open to the outside world. In days gone by, port 23 was always open and you could just telnet mycomputer and go right to your command line:
Unfortunately, root users can type things like “RM minus RF splat” (rm -rf *), which stands for remove recursively forcibly all files.
So, port 22 is out and port 23, secure shell, is in. It’s the exact same thing. As a bonus it’s the only way to communicate with your instance at the beginning, until you get your software configured. The other two open ports are 80, http, and 443 https. These are useless until you get the web server configured and running.
I don’t know what ICMP -1 is. It is “kind of” an umbrella term for all ports, so it might mean all ports are turned off unless specifically turned on in the list above.
So, need to create an instance, and set up to talk to it via secure shell, called SSH in linux world and Putty in Windows.
But first, key generation…