Tone is the attitude of the author toward the subject. Writers develop tone with word choice and how they choose to describe characters, places, and events.
Writers can develop many different kinds of tone when writing about different subjects. The tone can be humorous, serious, sarcastic, sad, amused, formal, informal, etc. Again, the tone is the attitude of the writer, and it is conveyed through word choice and the information that the writer chooses to share.
A writer who chooses to describe a visit with Santa Claus, and tells us about how Santa's breath smelled and he fell off of Santa's lap would have a humorous tone.
A writer who is describing a visit to the town of Gettysburg, PA, who chooses to tell us about how she walked where Civil War soldiers bled and died for others to be free would have a serious or even sad tone.
Examples of Tone from Literature
In A Modest Proposal Jonathan Swift has a satirical tone as he describes how the English could deal with the overpopulation and starvation of people in Ireland. They could just eat the babies:
A child will make two dishes at an entertainment for friends; and when the family dines alone, the fore or hind quarter will make a reasonable dish, and seasoned with a little pepper or salt will be very good boiled on the fourth day, especially in winter. I grant this food will be somewhat dear, and therefore very proper for landlords, who, as they have already devoured most of the parents, seem to have the best title to the children.
In his poem, "The Road Not Taken," Robert Frost has a nostalgic and reflective tone as he thinks back to a life-changing decision to take the "road less traveled."
Two roads diverged in a yellow wood,
And sorry I could not travel both
And be one traveler, long I stood
And looked down one as far as I could
To where it bent in the undergrowth;
Then took the other, as just as fair,
And having perhaps the better claim,
Because it was grassy and wanted wear;
Though as for that the passing there
Had worn them really about the same,
And both that morning equally lay
In leaves no step had trodden black.
Oh, I kept the first for another day!
Yet knowing how way leads on to way,
I doubted if I should ever come back.
I shall be telling this with a sigh
Somewhere ages and ages hence:
Two roads diverged in a wood, and I-
I took the one less traveled by,
And that has made all the difference.