Tone is all about how an author treats the subject of a text and the audience. The two most common categories for tone
are “formal” and “informal,” but other words to describe it abound. “Solemn,” “friendly,” “sarcastic,” “condescending,” and “enthusiastic” are a few other examples.
Tone is sometimes confused or used interchangeably with mood; but they are different concepts. Tone is about the author’s attitude as expressed by things like diction, syntax, and point-of-view. Mood is about how a piece of writing affects the audience. So, tone has an influence on mood of a piece, and there are many words that can be used to describe both (somber, for example).
Many other aspects of a piece of writing can affect tone, including the amount of detail an author employs (see images), the sounds of the words themselves (see euphony), the level of specialization in the chosen vocabulary (see jargon), and the overall pace of the piece.
Sometimes it’s difficult to tell exactly what sort of tone you’re setting, and sometimes different readers will read the same words and interpret their tone differently. For example, sometimes it’s hard to distinguish “passionate” from “angry.” The only way to really be sure about the tone of a piece of writing is to have other people read it and give you feedback.