In CSS there are all kinds of font families...there are generic family names like serif, cursive, sans-serif, monospace, fantasy, etc.; but the font-family names are times, arial, courier, etc.
So, ideally the font would be installed, if not, DC asks Windows to look to a font in the font family, if that isn't possible, into the generic family, and if none there, the system font is used.
Here are a couple of pages with good articles that explain it like I did and kind of like I did, respectively.
http://www.w3schools.com/CSS/pr_font_font-family.asp
http://webdesign.about.com/od/fonts/a/aa080204.htm