In typography, emphasis is the strengthening of words using a font in a different style from the surrounding text. This includes italic, bold, underlined, and strikethrough typefaces.
The italic type is a cursive font based on a stylized form of calligraphic handwriting. You can use italics to emphasize important points, write the titles of certain creative works, cite foreign words, or quote a speaker.
A bold font weight makes the letters thicker than the surrounding text. It is often used to highlight keywords. For example, entries in printed dictionaries are usually marked in bold.
Professional typesetting rarely underlines words for emphasis. Doing so is considered too distracting. Underlining is, however, often used with typewriters, in handwriting, and with some non-alphabetic scripts.