The SAT (Scholastic Assessment Test) is a standardized exam used for college admissions in the United States. It assesses a student's skills in Reading, Writing, and Mathematics. The test helps universities evaluate a student's readiness for undergraduate programs.

There are no strict eligibility requirements for the SAT exam. It is generally taken by high school juniors or seniors, or students planning to apply for undergraduate programs. The exam is open to all students regardless of nationality or educational background.

You can apply for the SAT exam through the College Board website. You need to create an account, select your exam date, test center, and fill in the required information. Payment for the exam can also be made online during the registration process.

The SAT exam consists of three main sections:

• Evidence-Based Reading and Writing (Reading and Writing & Language)
• Mathematics (with and without a calculator)

There is also an optional Essay section, which is no longer required by many colleges. The exam lasts for 3 hours, plus an additional 50 minutes for the Essay section if taken.

The SAT covers the following areas:

• Reading: Comprehension of passages from various subjects like literature, social studies, and sciences.
• Writing and Language: Grammar, sentence structure, and punctuation.
• Mathematics: Algebra, geometry, data analysis, and problem-solving.
• Essay (optional): Analyzing and evaluating a given argument.

The SAT exam is scored on a scale of 400 to 1600, combining the scores from the Reading and Writing and Mathematics sections (each worth 200 to 800 points). The Essay section is scored separately. A perfect score is 1600.

The registration fee for the SAT exam is generally $55 for students in the United States. Additional fees may apply for the optional Essay section, late registration, or changing test centers. International fees may vary.

The SAT is offered several times a year, typically in March, May, August, October, November, and December. Specific test dates can be found on the official College Board website.

Some recommended books for SAT preparation include:

• "The Official SAT Study Guide" by College Board
• "Kaplan SAT Prep Plus" by Kaplan
• "Barron's SAT" by Barron’s Educational Series
• "Cracking the SAT" by The Princeton Review

To improve your SAT score:

• Take timed practice tests to build test-taking stamina.
• Focus on weak areas through targeted practice.
• Review fundamental concepts in math, reading, and grammar.
• Work on time management to ensure you finish all sections within the allotted time.