On Linux, Windows and basically every other OS you can think of, there is a need to manage users. Those users can access the system and use its resources. In our case, we're managing users that are going to be connecting remotely, over SSH.
As you know by now, we're using Ubuntu Linux. That means these commands may not translate perfectly to another distribution. They most certainly won't translate to Windows at all.
The users we're going to be creating are normal, non-privileged users. They won't be able to install software (at the system wide level), manage services, and the usual stuff the
root user was doing.
We'll also create a group too. A group contains users. Assigning permissions to a group assigns those permissions to a user inside of the group.