A command is something I shout to an underling or my shell prompt. My shell interpreter takes my command, parses it and calls the necessary tool, be it a builtin or an executable.
I tell Tom to fetch the morning paper from the yard. Is Tom a command? No, Tom is my son.
I remember a moment in an early job interview. My resumé was all proper for this entry level junior position and everything was checking out. We turned to smalltalk to round up the interview.
"What sort of music do you like?"
(What sorta ques... you don't just throw this in without a warning. ahh I'm blanking out. What was it that I listened to last night??)
"Uhhh Mike Oldfield is one..."
"Ohh... (pause) ewww. But we won't let this hinder your application heh heh"
"hee..."
I got the position and rose to senior rather quickly. I didn't have any interactions with this guy since after this one interview. Maybe for the best. He didn't mean bad, he was just a bit out of his element 2nd-seat interviewing for devs.
I tell Tom to fetch the morning paper from the yard. Is Tom a command? No, Tom is my son.