The ASVAB, Armed Services Vocational Aptitude Battery, is an aptitude test that measures developed abilities and helps predict future academic and occupational success. Your scores on the other ASVAB composite tests will determine your career field or military occupation eligibility. Since enlistment bonuses usually are tied to your choice of occupations, the better the score, the more opportunities you have. ASVAB Practice tests are abundant online. 

From Military.com