GPP is general physical preparedness and SPP is special physical preparedness. Lots of info on each of those in the articles at elitefts, and also in the training forum.
It's not periodization, but in a way it is. It's self-periodizing. The idea is that you will be able to train at 100% of your max week after week without overtraining if you constantly switch up your ME movements. So in essence, it's periodized into 1-week mini-cycles.