In typography, a serif (/ˈsɛrɪf/) is a small line or stroke regularly attached to the end of a larger stroke in a letter or symbol within a particular font or family of fonts.

Font Family in CSS

font-family: Constantia, "Lucida Bright", Lucidabright, "Lucida Serif", Lucida,
  "DejaVu Serif", "Bitstream Vera Serif", "Liberation Serif", Georgia, serif;