StyleForm[expr, options] prints using the specified style options.
StyleForm[expr, "style"] prints using the specified cell style in the current notebook.
You can use font options such as FontSize, FontWeight, FontSlant, FontFamily, FontColor and Background in StyleForm.
Additional options can be given as in StyleBox.
StyleForm acts as a "wrapper", which affects printing, but not evaluation.
StyleForm can be used to specify the style for text in graphics.
StyleForm[expr, "style"] will work only if the notebook front end is being used; StyleForm[expr, options] for many options will work in all cases.
When StyleForm objects are nested, the options of the innermost one control the printing of a particular expression.
See The Mathematica Book: Section 2.8.9 and Section 2.9.15.
See also: StylePrint, StyleBox, TextStyle, $TextStyle, FormatType, Cell.