Advanced Placement courses culminate in an exam (which is optional unless a student is in a district that requires all of its AP students to sit for the exam). The exams are scored and a qualifying score means that colleges and universities can give credit for certain courses if they so choose. Colleges don't have to accept AP credit at all. Most do though, recognizing that students who have successfully qualified on the exams, which are incredibly rigorous, have met the requirements for comparable courses in their institutions.

So for instance, my students take the AP English Language & Composition exam. The course focuses on rhetorical analysis, persuasion, and argumentation. Generally, qualifying on this exam can earn 3 or 6 hours of freshman level rhetoric and composition credit depending on how high a student's qualifying score is and what the individual universities choose to give credit for -- it varies.