What were the distinguishing characteristics of Brechtian theatre?

Brecht was one of the pioneers of the "Political Theatre" which was a way to criticize modern political happenings through theatrical plays. Brecht believed the best way to get the audience to question their surroundings and the reality they were a part of was to make it obvious that what they were seeing was a play, so as not to lose the audience to a feeling of fantasy. To do this he used the famous "alienation effect" which prevents the audience from becoming too immersed in the story and instead approach the story and characters with a critical point of view. Examples of this include the use of projections, a narrator, harsh lighting, minimal set, lack of names for the characters, and the use of song ironically. Actors should portray the characters but never become them. 

Brecht also believed in "gestus" which is a form of acting which portrays only the character's social relations, focusing on exterior aspects of the character instead of the development of his psychological or emotional aspects. This can be done through narration or simply through a kind of mime technique.