Amy Mayer provides a chart outlining what she sees as the differences between Projects and PBL.
Problem-based learning and project-based learning provide a rich opportunity for students to deepen their knowledge, expand their repertoire of technical skills, and enhance their appreciation of thinking tools, processes and strategies. The larger goal is for enhanced performance under challenging conditions that demand strategic reasoning, insightfulness, perseverance, creativity, and craftsmanship to resolve complex problems.
"In Project Based Learning (PBL), students go through an extended process of inquiry in response to a complex question, problem, or challenge. Rigorous projects help students learn key academic content and practice 21st Century Skills (such as collaboration, communication & critical thinking)."
Information adapted from the Buck Institute for Education's (2011) PBL in the Elementary Grades: Step by Step Guidance, Tools, and Tips for Standards-Focused K-5 Projects