'Command not recongnised' in console

Language Help Rails
1

I’m stuck because of a strange bug.
The only command that works in command line is ‘rails new TravelApp’, it indeed creates new app. Other than that - anything gives ‘command not recognized’ like this:

$ ls
command not recognized
$ cd
command not recognized
$ rails
command not recognized

Any idea what to do with this situation?

2

Suggest to rest exercise.