_ Old Style- typefaces from the 14th and 15th century rooted in the renaissance, they from have a low level of contrast and a friendly appearance. Their emulation of calligraphy hurts the print quality of this class vs other fonts designed for print. Garamond would be an example of this class with rounded serifs that are bracketed.
_ Transitional- Sharper seriffing and a stronger vertical than the old style these fonts were a bridge used in the transition to copper and wood. Baskerville is an example of this class.
_ Modern- Were much more dynamic than previous generations combining slab serifs and the use of different line stroke weights. Bodoni is an example of the high contrast font class.
_ Slab Serif- A type class used in advertising in the late 19th and early 20th key characteristics are the strong square ended serifs. Fonts in this class can range from dense to light but most maintain a high readability even at distance and have a strong presence on the page.
_ Sans Serif- Also refereed to as grotesk these fonts were developed for the press and were influenced by the bauhaus movement in Germany. They forgo seriffing for a much cleaner over all effect. This is by far the most commonly used font class currently due to the high legibility and relatively benign nature. Helvetica and Univers are the most common examples of the class.
_ Script- This font class emulates the handwritten word and has a lower contrast and light presence on the page. The stroke usually has a dynamic width and is closest to actual calligraphy of all classes.
_ Blackletter- Highly ornamental based on the work of scribes for the illuminated manuscripts this font if highly dynamic in it's use of stroke weight and ornamentation of the individual letters. The overall contrast on the page is pretty low though. Old English is an example of the class as well as the type face used for the mast head of the New York Times
_ Grunge- Distressed typefaces featuring a worn and abused look. The use of these is more common in screen printing and posters where the increased size offers better legibility. 28 Days Later is one of my favorites from this class.
Here is a link to a list of this designers top 60.
_ Monospaced- these fonts were developed first for the typewriter and then used on computers and are still used in terminal applications. Each character uses the same amount of space. These fonts therefore are great for technical applications but do not offer the same variation of color on the page that a non monotype would offer. You can find many monospace variation of the other font classes.
_ Undeclared- is a catch all for those fonts that escape they previous categories. And all my searches have given me nothing other than that short answer.
There are of course many subsets in each class depending on how far you want to go into this.
