"PredictionX" is the name of the online project created at Harvard, by the HarvardX organization, hosted on the edX platform. The entries in this section of predictionx.org offer direct links to already-released content from the online project, as well as to content still under development.
We encourage you to start with The Framework for Predictive Systems in order to better understand the project's pedagogy. From there, you will find resources related to specific parts of PredictionX (such as The Diviner's Guide and The Tools of the Navigator in Lost Without Longitude).
To get a good idea of what the full PredictionX effort at Harvard is about, and how it started, try watching this talk by Prof. Goodman, if you have 50 minutes.