Do all Linux programs have some kind of terminal command as well? Its seems many that I use do. And many seem like terminal commands can actually be more effective sometimes.

I was just wondering if it was always programmed in to software to allow terminal commands for any given software. Like, could you pick up anything and use it fully in a terminal? (Like a messenger) I am getting the idea that it's up to the developer. If they want to incorperate the commands, they can, if not, they just have it as a GUI program. I just wasn't sure how it all worked.