Theatre is a performing art together with drama, comedy, music, motion pictures, opera and dance. It refers to acting stories in front of a group of people called audience. This is done by combining different movements, gestures, vocal modifications, dance, music, lights and any other type of performing art can be included. Also, you have to know that theatre developed itself in other categories of entertainment like ballet, mime, pantomime and Chinese opera.
Theatre is very complex. We can actually say that parts of it allow infinite modifications and ideas to be implemented. Actors have a very good training behind them that is necessary to learn how to act. This is because there are certain actions and methods of speaking that are not done like in real life. For example you can be a great orator but you may not be a good actor because you lack the proper training to back the speaking skills with movement. When acting a play you have to speak louder and connect differently with people.
The audience sees the play but there is much more to a theatre show than what one sees. Behind the scenes one can find a crew of people that is in most occasions even bigger than the actors playing. That crew is formed of the director, the sound and light engineers, the costume and scene creators and many more. These are the people we don't usually see and only some of them become famous.
There are many ways to write a theatre play can be done in many ways. We can even say that every author has his own style and also, the good actors will have a specific way of acting. The play in itself needs to have a plot, characters, ideas, songs, language and spectacle. This thought was first mentioned by Aristotle, who was the first to categorize the needed parts of a play. Nowadays we can easily notice that sometimes some of these have been taken out. A good example is given by absurd theatre, which seemingly has no narrative thread and no idea. Many people enjoy acting them because they allow an almost infinite freedom in how it can be analysed and acted.
Theater or theatre?
In American English people 'theater' is more commmonly used than its British counterpart, except when the word refers to building in which a performance takes place. Professionals generally use “theatre”.