MORE ON FRAGMENTS

Simplest example: a point primitive generating a single fragment whose associated pixel is the obvious one -- this is the pixel where you might display the point.
-- The color of the fragment depends on the color attributes and vertex normal of the point, and state information such as ambient light.

In general, a pixel might have many fragments (including no fragments) associated with it.
-- The graphics pipeline uses a variety of techniques (depending user-specified parameters) to determine a single color attribute for the pixel, from these associated fragments.

E.g., a fragment may have a depth value, and if the z-buffer is turned on, this depth value will be used to decide whether to discard the fragment or to replace the current colors at the associated pixel.