Video Courtesy of (site-affiliate) Kaplan GRE prep.
The GRE Verbal and Quant sections are each divided into two parts. The first parts are of medium skill level. If you score highly, on your first Verbal section, then you will get a harder second Verbal section. If you scored poorly on your first Verbal section, then your second Verbal section will be easier. The same process repeats for the Quant section. The GRE adapts to your performance on the first two sections of the test.
Harder Questions Count More
The result of the CAT testing format is that the harder problems count more than easier ones. If you get into the “hard” section, you will have the opportunity to get a very high score. Students stuck in the easy sections might end up getting more questions correct in the second half of the test, but they will still get a low score because the easy sections don’t award as many points as the hard sections.