Armed Services Vocational Aptitude Battery are tests that determine enlistment eligibility and aptitude for specific military jobs. The Armed Forces Qualification Test is a compilation of scores from the math and verbal portions of the ASVAB test, which is also used to determine enlistment eligibility and placement in jobs. Additionally, a separate Assessment of Individual Motivation test designed by the Army Research Institute is used to measure an applicant's motivation to serve in the armed forces.
For the record (and to get LadyX and COBI back as buds) in spite of what is often portrayed by Hollywood and the media, there aren't many 'slow' folks in the military, in any branch. The current generation of troops are, for the most part, amazingly sharp.
The ASVAB isn't meant to be a pass or fail test, just an indicator of basic abilities. But getting into the services isn't as easy as many folks seem to think. I talked with my youngest's Army recruiter during September and asked if apllications were up because of 9/11. He said they were, but the acceptance rate really hadn't changed because many were applying again after already being turned down before (criminal records pretty much keep one out, but the most common problems were medical). It's to their credit that the services have kept their standards fairly high even in these times of tough recruiting (my rant about those unwilling to risk their tender behinds to serve is a seperate issue...).