Style allows an abbreviated form of some options. For options such as
FontSize,
FontWeight,
FontSlant and
FontColor, you can include merely the setting of the option.
If you use the notebook front end for
Mathematica, then each piece of output that is generated will by default be in the style of the cell in which the output appears. By using
Style[expr, "style"] however, you can tell
Mathematica to output a particular expression in a different style.
"
Cells as Mathematica Expressions" describes in more detail how cell styles work. By using
Style[expr, "style", options] you can generate output that is in a particular style, but with certain options modified.