Two major generic font categories

Sans-serif text example
The lawnmower mowed the lawn.
Lilly Lilliput likes lillies.

Serif text example
The lawnmower mowed the lawn.
Lilly Lilliput likes lillies.

Three minor generic font variants

Monospace text example
The lawnmower mowed the lawn. (29 characters)
Lilly Lilliput likes lillies. (29 characters)

Cursive text example
The lawnmower mowed the lawn.
Lilly Lilliput likes lillies.

Fantasy text example
The lawnmower mowed the lawn.
Lilly Lilliput likes lillies.

Sans-serif font samples

Arial: Sphinx of black quartz, judge my vow 0123456789
Tahoma: Sphinx of black quartz, judge my vow 0123456789
Trebuchet: Sphinx of black quartz, judge my vow 0123456789
Verdana: Sphinx of black quartz, judge my vow 0123456789
Comic Sans MS: Sphinx of black quartz, judge my vow 0123456789

Serif font samples

Garamond: Sphinx of black quartz, judge my vow 0123456789
Georgia: Sphinx of black quartz, judge my vow 0123456789
Times New Roman: Sphinx of black quartz, judge my vow 0123456789
Rockwell: Sphinx of black quartz, judge my vow 0123456789
Book antiqua: Sphinx of black quartz, judge my vow 0123456789
Bookman Old Style: Sphinx of black quartz, judge my vow 0123456789
Courier New: Sphinx of black quartz, judge my vow 0123456789

Further font descriptions: http://shark.comfsm.fm/~dleeling/cis/fontdescriptions.html
The web page http://shark.comfsm.fm/~dleeling/cis/dropdown_style.html allows you try out a wide variety of fonts.