A written word can be dressed up basically in two kinds of fonts.
(1)Serif Fonts :Each of these words has structural details at the end of every stroke.
(2)Sans Serif Fonts :The edges of these words are smooth and contains no details.
While reading printed matter in news paper,magazines and books we prefer serif fonts.That is because the eye doesn't read individual words but scan over blocks of text.But it hates the shape that serif fonts form on a computer screen.So various sans serif fonts for electronic text came into existence, like Helvetica (owned by Linotype),Arial (owned by M$),Georgia etc.,
Vist this for 20 best license-free official-fonts.