Originally intended with breaks for the actors or speakers in mind, intermissions have come to be an opportunity the audience usually gets to eat some food and buy drinks, stretch their legs, and/or use the restrooms.
An intermission is also often billed as an entr'acte, a word that came from the French for something in between two acts.
A theatrical play or opera may have several intermissions, depending on its length. Movies have usually one intermission, sometimes two if they are very long.
See also: interquel