GRE
GRE is used to assess applicants' readiness for graduate school and their academic potential. Graduate schools use GRE results to compare applicants; however, not all programs regard GRE scores equally. Many programs do not require GRE scores while for others it may be mandatory.
GRE also helps a person analyze and determines his preparedness for a Graduate Degree and also his future. If you take up a GRE exam now, your test scores are valid for 5 years which means that you could take up the exam right now and apply for a great graduate school five years later.
GRE is compulsory in U.S Universities only. In USA some universities don't required GRE score :MIT ,UIUC , John Hopkins etc for CS. Many University don't required GRE, but they recommend to send GRE score if your GPA is not par. GRE score is not required in Canada or any other countries.
Syllabus:
The GRE syllabus is divided into three broad sections:
Analytical Writing Assessment: This section evaluates the test taker’s ability to critically scrutinize complex issues, analyse arguments and put forth their thoughts reasonably.
Verbal Reasoning: This section evaluates the examinee’s ability to read and analyse the written material in the standard English language. There are three types of questions under this section:
(1) Sentence Equivalence
(2) Reading Comprehension
(3) Text Completion
Quantitative Reasoning: This section evaluates the examinee’s knowledge of mathematical concepts like Algebra, Geometry, Arithmetic, Data Analysis, etc.