If you want to be an actor, there really is one thing that you have to do - you have to get in front of an audience.
Seems simple and obvious, doesn't it?
Ok, but there is more to it than that. You have to get in front of an audience, and you have to show them a story. While you are showing them, you have to find ways to invite them into that story with you. You have to connect with the audience and allow them to connect with you.
What is connecting? It's magic. It's magic that flows both ways, from the stage to the audience, and from the audience back to the actors. It's the art of theatre.
Magic is fickle. Connecting is not always easy. There is a certain critical mass that you need to enable the magic to flow back to the stage. Audience members need each other to feel sufficiently anonymous, so that they are safe and can be open to the magic. It's pretty potent stuff. Not for the faint of heart.
Audiences can sill get a 'good show' without the magic. They just can't get a great show. Without magic, they will come away being entertained. They will have understood the story, but they will not have an emotional response to the work. Masterful, competant technique can tell a good story, but only magic can allow someone else to live it.