Project based learning and problem based learning are two didactic approaches to learning that are often used interchangeably to refer to the same thing: engaging students in authentic learning activities. This truism does not always hold true. In a learning task that is problem based, the focus is on finding solutions to the problem posed through applying learned strategies and in so doing the process of arriving at the solution is, in and of itself, an integral part of the overall learning taking place . Whether a learning activity is authentic or not does not really matter from a problem based learning perspective because often times 'fictitious scenarios' are purposefully designed to provide learners with a contrived environment to work on their ill-structured problems.
Via Elizabeth E Charles