GRE(Graduate Record Examinations):-

GRE is an exam which is a pre-requisite to get admissions to most universities in the USA. It tests your general awareness, reasoning capability and communication skills as a whole. It does not involve any engineering specific syllabus, as it undertaken by everyone who is applying for graduate admissions in the USA(and some European countries). There are no rankings involved and its only your score that matters.
Target audience: Prospective graduate students across all disciplines.
Required by: Graduate schools and departments.
Purpose: GRE scores are used to assess the suitability of applicants for graduate-level study across many different subject areas. Some departments may ask applicants to take one of the GRE Subject Tests, while others require the General Test. The Subject Tests assess knowledge in a particular field, while the General Test assesses verbal reasoning, quantitative reasoning and analytical writing.
Verbal Reasoning:-Measures your ability to analyze and evaluate written material and synthesize information obtained from it, analyze relationships among component parts of sentences and recognize relationships among words and concepts.
Quantitative Reasoning:-Measures problem-solving ability, focusing on basic concepts of arithmetic, algebra, geometry and data analysis.
Analytical Writing:-Measures critical thinking and analytical writing skills, specifically your ability to articulate and support complex ideas clearly and effectively.
Duration: Around three hours and 45 minutes (six sections with a 10-minute break after the third).
Cost: US$205 everywhere except China, where it is $220.70.
Valid for: Five years.
Points to note: The GRE is only delivered in English. A paper-based version is offered at centers where the computer-based test cannot be delivered. Candidates sitting this version are allowed slightly longer for the Verbal and Quantitative sections.