I came across an interesting Blog post today that articulated the difference between these three approaches. Many use the labels interchangeably. I have used all three - noting the subtle differences, however found this post to be short and succinct in articulation. There is a distinct difference between the three that makes them suited to different tasks and subject areas, with at times, quite different outcomes.
If you have ever wondered what the difference is, that a look at this blog post on Fluency 21
http://fluency21.com/blog/2013/03/14/should-i-teach-problem-project-or-inquiry-based-learning/
