In Elizabethan drama (as in Shakespeare's Henry V [1598-99]), "chorus" refers to a single character who appears as needed for narrative purposes, for instance speaking the prologue and epilogue. In modern criticism, a choral character is someone within the play's action but largely aloof from it, who either views the action in a unique way (often with irony) or represents a particular type of perspective.
In Shakespeare's Hamlet (1600) and Antony and Cleopatra (1606-07) respectively, Horatio and Enobarbus can be seen as choric figures; Horatio offers Hamlet a steady moral perspective, while Enobarbus is appreciative and ironical but also represents the perspective of the proud and staunch Roman soldier.
"Chorus" can also be used as a synonym for refrain, meaning the repeated lines or stanzas in a song.