So the first thing which I recommend for everyone who are new to GMAT is to carefully and slowly go through the sections overview and understand what exactly you will be tested for and the type of questions you will be asked.
I can explain it in my own words, but it would be prudent to hear what the makers of GMAT have to say :
P.S. - All text below is from MBA.com.
Analytical Writing Assessment Section
The AWA consists of two 30-minute writing tasks—Analysis of an Issue and Analysis of an Argument.
The issues and arguments presented on the test concern topics of general interest related to business or a variety of other subjects. A specific knowledge of the essay topic is not necessary; only your capacity to write analytically is assessed.
Analysis of an Issue
For the Analysis of an Issue section, you will need to analyze the issue presented and explain your point of view on the subject. There is no correct answer. Instead, you should consider various perspectives. Use relevant reasons or examples drawn from your experience, observations, or reading to develop your own position on the issue.
What Is Measured
The Analysis of an Issue tests your ability to explore the complexities of an issue or opinion and, if appropriate, to take a position that is informed by your understanding.
Analysis of an Argument
For the Analysis of an Argument section, you will need to analyze the reasoning behind a given argument and write a critique of that argument. You are not being asked to present your own views on the subject.
Consider the following when developing your essay:
- What questionable assumptions underlie the thinking behind the argument?
- What alternative explanations or counterexamples might weaken the conclusion?
- What sort of evidence could help strengthen or refute the argument?
What Is Measured
The Analysis of an Argument section tests your ability to formulate an appropriate and constructive critique of a specific conclusion based on a specific line of thinking.
Quantitative Section
The Quantitative section of the GMATmeasures the ability to reason quantitatively, solve quantitative problems, and interpret graphic data.
Problem-Solving and Data-Sufficiency questions are intermingled throughout the section. Both types of questions require knowledge of:
- arithmetic,
- elementary algebra, and
- commonly known concepts of geometry.
Problem-Solving Questions
Problem-Solving questions are designed to test:
- basic mathematical skills,
- understanding of elementary mathematical concepts, and
- the ability to reason quantitatively and solve quantitative problems.
Data-Sufficiency Questions
Data-Sufficiency questions are designed to measure your ability to:
- analyze a quantitative problem,
- recognize which information is relevant, and
- determine at what point there is sufficient information to solve a problem.
Data-Sufficiency questions are accompanied by some initial information and two statements, labeled (1) and (2). You must decide whether the statements given offer enough data to enable you to answer the question. You must choose one of the following answers:
- Statement (1) ALONE is sufficient, but statement (2) is not sufficient.
- Statement (2) ALONE is sufficient, but statement (1) is not sufficient.
- BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
- EACH statement ALONE is sufficient.
- Statements (1) and (2) TOGETHER are NOT sufficient.
Verbal Section
The Verbal section of the GMAT exam measures your ability to:
- read and comprehend written material,
- reason and evaluate arguments, and
- correct written material to conform to standard written English.
Reading Comprehension Questions
Reading Comprehension passages are up to 350 words long. Topics contain material from the social sciences, physical or biological sciences, and business-related areas (marketing, economics, human resource management, etc.).
Because the Reading Comprehension section of the GMAT exam includes passages from several different content areas, you may be generally familiar with some of the material; however, no specific knowledge of the material is required. All questions are to be answered on the basis of what is stated or implied in the reading material.
Reading Comprehension passages are accompanied by interpretive, applied, and inferential questions.
What Is Measured
Reading Comprehension questions measure your ability to understand, analyze, and apply information and concepts presented in written form.
This section evaluates the following abilities:
- Understanding words and statements in reading passages: Questions of this type test your understanding of and ability to comprehend terms used in the passage and your understanding of the English language.
- Understanding the logical relationships between significant points and concepts in the reading passages: Questions of this type ask you to determine the strong and weak points of an argument or to evaluate the importance of arguments and ideas in a passage.
- Drawing inferences from facts and statements in the reading passages: Questions of this type ask you to consider factual statements or information and, on the basis of that information, reach a general conclusion.
- Understanding and following the development of quantitative concepts as they are presented in verbal material: Questions of this type involve the interpretation of numerical data or the use of simple arithmetic to reach conclusions about material in a passage.
Critical Reasoning Questions
Critical Reasoning questions are designed to test the reasoning skills involved in making arguments, evaluating arguments, and formulating or evaluating a plan of action. Questions are based on materials from a variety of sources. No familiarity with the specific subject matter is needed.
What Is Measured
This section measures your ability to reason effectively in three areas:
- Argument construction: Questions of this type may ask you to recognize the basic structure of an argument, properly drawn conclusions, underlying assumptions, well-supported explanatory hypotheses, or parallels between structurally similar arguments.
- Argument evaluation: Questions of this type may ask you to analyze a given argument, recognize factors that would strengthen or weaken an argument, reasoning errors committed in making an argument, or aspects of the methods by which an argument proceeds.
- Formulating and evaluating a plan of action: Questions of this type may ask you to recognize the relative appropriateness, effectiveness, or efficiency of different plans of action; factors that would strengthen or weaken a proposed plan of action; or assumptions underlying a proposed plan of action.
Sentence Correction Questions
Sentence Correction questions ask you which of the five choices best expresses an idea or relationship. The questions will require you to be familiar with the stylistic conventions and grammatical rules of standard written English. You must also demonstrate your ability to improve incorrect or ineffective expressions.
What Is Measured
This section tests two broad aspects of language proficiency:
- Correct expression: A correct sentence is grammatically and structurally sound. It conforms to all the rules of standard written English, e.g., noun-verb agreement, pronoun consistency, pronoun case, and verb tense sequence. A correct sentence will not have dangling, misplaced, or improperly formed modifiers, unidiomatic or inconsistent expressions, or faults in parallel construction.
- Effective expression: An effective sentence expresses an idea or relationship clearly and concisely, as well as grammatically. This does not mean that the choice with the fewest and simplest words is necessarily the best answer. It means that there are no superfluous words or needlessly complicated expressions in the best choice. In addition, an effective sentence uses proper diction—the standard dictionary meanings of words and the appropriateness of words in context. In evaluating the diction of a sentence, you must be able to recognize whether the words are well chosen, accurate, and suitable for the context.
