Who has not ever wanted to know all the commands that exist in our system?
Well, here is another one who had this curiosity… and as is logical since I like to share, I share with you how to list all the commands available in the system 
compgen -c
Ok, this will do 
In the terminal all the available commands will be shown, if you wish you can save these commands in a text file to review it calmly:
compgen -c >> comandos.txt
Like, you can see with the parameter -a all alias:
compgen -c
Well… this is something extremely simple, but I hope it is useful to you 
regards
PD: See compgen help (help compgen) for more options.