Italics is the modern-day version of underlining. It is sloped writing used for emphasis. There are certain situations where italics is used in writing.
Direct internal discourse (unspoken thoughts): Direct thoughts, imagined dialogue, and other interior monologue, when expressed in the first-person point of view, are typed in italics. Example:
Stephanie shook her head and thought, What am I going to do with him?
Indirect thought: interior thought that is paraphrased should not be italicized. An example would be:
Stephanie told herself that she needed to tell him the truth.
Titles of books, movies, songs, and newspapers
Foreign words: Foreign words and phrases should be in italics if they are likely to be unfamiliar to most readers, particularly for the first occurrence with in the book. If it is a fairly common word, italics is often unneeded.
Letters used as letters: Individual letters of the alphabet are italicized, unless they are used in a common expression. Examples include:
the letter T
Justin signed the paperwork with an X.
Be sure to dot your i's and cross the t's.
Words used as words: Words used as words, or phrases used as phrases, should be italicized. Examples include:
"Why is it so hard for you to say I'm sorry?"
"The word resign has multiple meanings," Amanda said.