Abstract reasoning tests require the ability to draw assumptions and conclusions based on information supplied in the form of symbols or matrices. On these tests, you are asked to identify a missing item or diagram that completes a certain pattern of logic.
Simply put, an abstract reasoning/abstract thinking test is used to assess one’s ability to understand and analyze visual information through pattern recognition, as well as one's ability to generate hypotheses, change tracks, and critically evaluate. By utilizing shapes and images to depict specific logic patterns and/or processes, these tests are able to measure general intelligence, abstract thinking skills, and how well you can problem solve.
In addition, these tests do not contain numbers or words. Rather, the questions are based on patterns of provided shapes.
Another reason why abstract reasoning tests are so common is because these tests aim to minimize cultural and educational dependencies in order to provide an objective indication of intellectual potential.