What does it mean to refer to the "voice" in a piece of literature?

The "voice" in works of literature can refer to two different things. One is the author's style and what makes him unique and distinct. The other is the character-specific speech and thought patterns of the main character.

Every author writes with a certain style that is unique and often flows into the protagonist. These different styles help create characters and set moods in written work. A story might be told in the "voice" of a child or the "voice" of a politician, even though the author is neither. Voices in literature are not to be confused with the voices in writing, which are referred to as active and passive voice.