"Students work on a project over an extended period of time – from a week up to a semester – that engages them in solving a real-world problem or answering a complex question. They demonstrate their knowledge and skills by developing a public product or presentation for a real audience.
As a result, students develop deep content knowledge as well as critical thinking, creativity, and communication skills in the context of doing an authentic, meaningful project. Project Based Learning unleashes a contagious, creative energy among students and teachers."taken from: http://www.bie.org/about/what_pbl
ISTE - Empower Learners through Project-based Learning
Problem based learning or Project based learning?
"One could argue that completing any type of project involves solving a problem. If students are investigating an issue -- say, immigration policy -- the problem is deciding where they stand on it and how to communicate their views to a particular audience in a video. Or if students are building a new play structure for a playground, the problem is how to build it properly, given the users' wants and needs and the various constraints of safe, approved construction. Or even if they're writing stories for a book to be published about the Driving Question "How do we grow up?", the problem is how to express a unique, rich answer to the question.
So the semantics aren't worth worrying about, at least not for very long. The two PBLs are really two sides of the same coin. What type of PBL you decide to call your, er . . . extended learning experience just depends on how you frame it. The bottom line is the same: both PBLs can powerfully engage and effectively teach your students!"--taken from John Larmer, Buck Institute of Education