Characterization
Beginner
Testing a new chip at every speed, voltage and temperature it might face, to find the limits it can safely be sold with.
Novice
Detailed measurements of timing, current and voltage levels on a statistically meaningful sample of chips, across combinations of conditions, to find the real operating limits and to build the shorter test that every production chip will get.
Expert
Its outputs are data-sheet limits with a safety margin (guard band) added, the bin definitions, and a production test program cheap enough to run on every part. It continues through production to track drift and improve yield.