The GRE is a computerized test that adapts to your performance. This format is called a CAT (computer-adaptive test). As you take the test, the computer will select questions based on your performance. If you get a question correct, the test may select a more difficult one next. If you get a question wrong, the computer may select an easier one next. Thus, the test adapts to your performance. The score you get also adjusts accordingly in the sense that the tougher your questions get, the higher you score.
Each computer-based test section meets pre-established specifications, including the types of questions asked and the subject matter presented. The statistical characteristics of the questions answered correctly and incorrectly, including their difficulty levels, are taken into account in the calculation of scores. Therefore, scores of all test takers can be compared even though they received different questions.