A general definition is that it is an edcuational approach that places the onus on the students to learn to acquire and integrate information versus the traditional didactic approach. Students start with a clinical case, identify/research relevant points, discuss with other students, and solve the question(s) produced by the case. It is an analytical process that helps students learn basic science subject matter on their own, with minimal teacher/professor involvement. The objectives, other than the acquisition of specific concepts, are to teach future physicians to efficiently research questions, problem solve, and to work both independently and jointly with others to solve clinical cases.
PBL varies greatly from one school to the next. Some have an entire curriculum based on this approach, others balance didactics with PBL, and others use it as window dressing to entice prospective students.
I personally love it. I prefer active participation in learning versus sitting passively/being talked at in a lecture hall. The process helps cement information and the clinical cases provide a context for understanding info and remembering. It also allows for the integration of concepts, whereas didactics don't do this well in my mind.
I'd be happy to share more specifics about my school's use of PBL if you have more questions/interest.
