Information Type Elements

EM
The <EM> element provides typographic emphasis, typically italics. While <EM> and <I> often give the same effect, use <EM> except where it is necessary in the text to refer to the formatting, as in "The italic parts are mandatory". This will help to ensure consistency between documents from various sources if (for example) the reader prefers to use color in place of italics for emphasis.
CITE
The <CITE> element specifies a citation. Sections tagged with the CITE element are typically rendered in italics.
STRONG
The <STRONG> element provides strong typographic emphasis, typically bold.
CODE
The <CODE> element indicates an example of code; typically rendered in a mono-spaced font. Do not confuse with PRE.
SAMP
The <SAMP> element indicates a sequence of literal characters.
KBD
The <KBD> element indicates text typed (keyboarded) by the user. It might typically be used in an instruction manual.
VAR
The <VAR> element indicates a variable name, and might typically be used in an instruction manual.
DFN
The <DFN> element indicates the defining instance of a term. New in 3.0.
Q
The <Q> element is used for a short quotation. It is typically shown enclosed in quotation marks as appropriate to the language context. For English these would be matching double or single quotation marks, alternating for nested quotes. The language context is set by the LANG attribute. New in 3.0.
LANG
The <LANG> element is used to alter the language context when it is inappropriate to do this with other character-level elements. New in 3.0.
AU
The <AU> element indicates the name of an author. New in 3.0.
PERSON
The <PERSON> element is used for names of people to allow these to be extracted automatically by indexing programs. New in 3.0.
ACRONYM
The <ACRONYM> element is used to markup acronyms. New in 3.0.
ABBREV
The <ABBREV> element is used to markup abbreviations. New in 3.0.
INS
The <INS> element is used for inserted text, for instance in legal documents. New in 3.0.
DEL
The <DEL> is used for deleted text, for instance in legal documents. New in 3.0.

An example:

This text contains an <em>emphasized</em> word.
<strong>Don't assume</strong> that it will be italic!
It was made with the <code>EM</code> element. A cite is
often italic and has no formally required structure:
<cite>Moby Dick</cite> is a book title.