A typical Windows application allows you to apply a maximum of four styles to a typeface: regular, bold, italic, and bold italic. You select the regular style from the font menu. For example, when you choose Book Antiqua from the font menu, you see the typeface Book Antiqua regular. Then, you select bold or italic styles by clicking a bold or italic button or by using a keyboard shortcut. For example, to specify Book Antiqua Bold, you select Book Antiqua from the font menu. Then, youo apply the bold style by clicking a bold button.
This process of specifying a particular font by selecting a related font and applying a style to that font is called font style linking.
Many applications on Mac OS, in contrast to Windows, list all the styles for a typeface within the font menu. For example, a type family like Book Antiqua appears in the font menu as Book Antiqua, Book Antiqua Bold, Book Antiqua Italic, and Book Antiqua Bold Italic.
If you use a Macintosh, this functionality gives you two ways to specify a particular typeface. You can directly select the typeface from the font menu. Or, you can select the regular version of the typeface from the font menu. The, you use style linking by applying bold or italic to the regular face. Either method gives you the font you need.