Theatre (British English and also American English), or Theater (mostly American English), has several meanings.
The word comes originally from the Greek Theatron, meaning roughly, 'a place to behold'. In American English, the word 'theater' can mean either a place where films are shown (this is also called a
'Theatre' can also mean the business of putting on plays. An actor might say "I am in the theatre business", or a writer might say "I write for the theatre", meaning that they write plays, rather than writing for movies or television shows.  
The first people we know created plays were the Ancient Greeks, about the year 500 B.C. They divided plays into two kinds:
These ancient Greek plays were performed outdoors in large amphitheatres, so that many people could see them. There were contests among the playwrights (people who write plays are called playwrights) and the winner would get a prize.
The Greeks had many brilliant ideas. They used mechanical devices like
In the 1500s, groups of
Other kinds of plays called Neoclassical Dramas and Neoclassical Comedies were also popular in Italy and in France at this time. These plays were written to copy the style of the plays from Ancient Greece and Rome.
At the end of the sixteenth century (before 1600), the traveling actors began to perform in fixed theatre buildings. This was the period when
His theatre was in London, England. It was called The
Plays including Shakespeare's were banned during the Protectorate'. After that, many more were written and acted.
After World War II, playwrights in Europe and the United States began doing plays in a new style called "Theatre of the Absurd." After seeing the horrors of war, these playwrights felt that all their old values had been destroyed. Playwrights such as
The "Theatre of the Absurd" plays have some of the same ideas that are found in the
The plays written in this style make people think about questions like "what is it like to be a person in the world?" and "what does it mean for a person to be free?" They are often filled with sad emotions, such as worry, fear, and thoughts about death.