The GRE (Graduate Record Examination) measures analytical writing, verbal, and quantitative skills that have been acquired over a long period of time and that are not related to any specific field of study.
The analytical writing section tests your critical thinking and analytical writing skills. It assesses your ability to articulate and support complex ideas, analyze an argument, and sustain a focused and coherent discussion. It does not assess specific content knowledge.
The verbal section measures your ability to analyze and evaluate written material and synthesize information obtained from it, to analyze relationships among component parts of sentences, to recognize relationships between words and concepts, and to reason with words in solving problems. There is a balance of passages across different subject matter areas: humanities, social sciences, and natural sciences.
The quantitative section measures your basic mathematical skills, your understanding of elementary mathematical concepts, and your ability to reason quantitatively and solve problems in a quantitative setting. There is a balance of questions requiring arithmetic, algebra, geometry, and data analysis. These are content areas usually studied in high school.