The Next Generation Science Standards (NGSS) are new national science standards based on the three dimensions of the NRC's Framework for K-12 Science Education, which can be seen in brief here, or in it's totality here.
The following may help to understand both the NGSS and the Framework:
How to read the NGSS (NGSS)
The NSTA guide to the Framework (NSTA)
The NGSS@NSTA Hub