The Buck Institute for Education had Common Craft create a short animated video that explains in simple language the essential elements of Project Based Learning (PBL). Common Craft does very good simple "explanations in plain English." This one takes on the essential elements of PBL.
PBL (which, unfortunately, is also the abbreviation for PROBLEM based learning, which is not the same thing) has many buzzworthy elements for "21st Century skills and competencies" like collaboration, communication, and critical thinking. It seems like the idea has a stronger hold in K-12 which assumes that what college professors want are those skills because they are integral to college success. That may be, but many college classrooms assume students come in the door with these skills or those skills are not really a part of the college classroom.
Take a look at "Project Based Learning Made Simple" and let me know what you think about the video, and your own use of PBL in K-12 or higher education.