There are many formatting tags. Some useful ones are
<b> ... </b>
<strong>... </strong>
<big>... </big>
<em> ... </em>
<i> ... </i>
<small> ... </small>
<tt> ... </tt>
They are used to format the following paragraphs.
This text is made bold with <b> ... </b>
This text is made strong with <strong>... </strong>
This text is made big with <big>... </big>
This text is emphasized with <em> ... </em>
This text is made italic with <i> ... </i>
This text is made small with <small> ... </small>
This is teletype text, often used to display program source code. The tag <tt> ... </tt> is used to format it.
This is subscript and superscript