<p>The AP tests are basically a set of tests administered by CollegeBoard (the SAT guys) every May. You'll have to go onto collegeboard.com and look for a center most suited to you. </p>
<p>Their significance can be in a number of ways:
*If you do well in AP subject that is not a part of your high school course load , you display your academic diversity and ability.
*If your grades are 'deflated' as they are in many Indian schools, it gives colleges a yardstick to judge your performance by...a conversion factor.
*If you do an AP for any subject that is more difficult/goes deeper than your what you're doing with the same subject at school, your extra effort will be appreciated.
*If your teachers don't particularly like you, and give you low predictive grades out of spite, getting a 5 on an AP for the same subject would demonstrate to the college that you are indeed proficient in it.
*Credits: This is not so much to do with admission, but is still the main purpose of the APs, so I think its relevant. You get 'credits' for 5s in APs in lots of colleges, and that means you can
(a) skip beginner courses
(b) graduate college faster AND/OR
(c) do more of the courses YOU like by skipping some of the core requirements. </p>
<p>Hope this helps :)</p>