We are all stage actors
Oh yes we are. You may not actually have walked the boards to perform (at least not since school), but every time we want to get our way by putting on an "act," we are "acting," and because it is for someone at a reasonable distance away from us-a "real" distance-it is stage acting.
The child wanting her own way who cries real tears, which are miraculously cleared when she gets it, is giving a particularly convincing "performance."
The stern authoritarian voice you put on when complaining about bad service in a shop is another.
The fawning words and actions we all go through when pulled over for speeding, and the subsequent fake smiles, comprise yet another performance aimed at a particular audience.
These are moments when we are using our words and bodies to convince someone of some emotion or thought that may not, in fact, be the literal truth of what we are feeling, but is the emotion we want the other person to believe we are experiencing. This is what stage actors do, too.
Very few of us-especially, funnily enough, screen directors-have experience in acting for the screen or know what the difference would be between this and the acting mentioned above.