
Christa A. answered 06/04/19
Columbia Publishing Course Alum, Writing Coach + English/ESOL Tutor
Active/passive voice, as Gene G. explained, is one way to talk about voice in ELA, but that's more about the grammar than the style.
Another way to talk about voice is, as Lauren H. detailed, more to do with authorial voice, which is the writing craft or style choices that an author makes in order to create a cohesive writing style--they are the craft choices that make a person able to instantly identify who the author is simply by reading a passage. However, I disagree with the examples that Lauren provided; angry, wistful, apologetic, nostalgic--those are all examples of tone, rather than voice.
Examples of voice would be, for instance, that many of the Romantic writers wrote with long sentences and often went on lengthy tangents and focused on emotion and nature in their content. Those stylistic choices created enough of a voice in those authors that we were able to identify a literary movement and call it "Romanticism." Each Romantic writer, in turn, has their own particular writing quirks, which can be tracked throughout their oeuvre. It's comparable to the stylistic choices Picasso made that make us able to look at a piece of artwork we've never seen before and say, "Oh, that must be a Picasso, because it's fragmented and strangely colored and the pieces of the face are in strange places." These are all part of the style known as Cubism, an artistic movement, but Picasso did things slightly differently than his fellow Cubists, say Gris.
I hope that helps!