The masks of ancient Greece often covered the entire face, with holes for the eyes and wide mouths allowing the actors to speak. They allowed theatrical performers to take on all manner of roles, permitting complicated plays to be performed with just two or three actors. Their exaggerated facial features let audiences recognize the emotions from far away.
Theater was more than entertainment in Greece; it also served as religious worship and as a way to honor the gods. The twin masks of comedy and tragedy--one laughing, one crying--developed to embrace the two principle genres of Greek theater. But they also represented the god Dionysus, a mercurial being associated with parties and inebriation. The theater was sacred to him, and the twin masks of comedy and tragedy encapsulated his dual nature.
In medieval Europe, masks appeared during the performance of religious mystery plays. Such plays told stories of man's sin and the difficulty of finding redemption. In order to convey the ugliness of the sins--and the various demons who perpetuated them--the masks were exaggerated and grotesque. The stylized emotions also helped convey the essence of the play to audience members who might not otherwise see clearly, much the way the Greek masks did.
During the Italian Renaissance, a different sort of drama mask emerged. Commedia dell'arte, a type of improvised tomfoolery intended to upend social conventions became extremely popular. The masks used during such productions depicted outlandish or ridiculous features--serving the same purpose as earlier masks--but their concealing nature added something different to the equation. Not only did it free performers to tackle dangerous subjects without fear of retribution, but its appearance also had a disorienting effect on those who watched it, creating a surreal atmosphere where nothing was quite what it seemed.
The Japanese art of Noh theater emerged in the 14th century, adopting stylized masks as part of an elaborate tradition. Noh belonged to the upper castes of Japan, and commoners could not learn its techniques. The masks were typically only used by the main character, though some supporting characters could adopt them from time to time. Often, the actor would switch masks to depict a change in the character's demeanor or as a way of showing his "true" internal self.