This document summarizes the history and key aspects of problem-based learning (PBL), an educational approach developed in the 1960s by Howard Barrow and colleagues at McMaster University in Canada. PBL places students in collaborative groups to discuss open-ended problems with multiple potential answers. The teacher acts as a facilitator rather than lecturer. Proponents argue PBL enhances skills like problem solving, critical thinking, and motivation while helping students apply knowledge to real-life situations. Potential criticisms include the time commitment required of teachers to develop effective questions and guide discussions.