Grey literature includes all types of publications that are not published commercially in books or journals. They could be conference procedings, government reports, clinical guidelines, statistical information and all sorts of other valuable information.
For Assessment 1 you have been asked to find health policies, initiatives and models of primary health care. You will need to find the originals of these policies (as well as the journal articles critiquing them). In addition, in the Background section you have to find some statistical information and impacts. Both these parts of the assessment would benefit from some good grey literature.
Have a look at the Health section of the Grey Literature Library Guide. Here you will find some great sources for guidelines and policies (in the first section, especially NICE, Guideline Central and Australian Clinical Practice Guidelines). For background information and statistics you can't go past WHO, AIHW and the Analysis & Policy Observatory. Check out some of the other links as well, there's so much great information here.
The Evaluation section of this guide is also helpful. If you are using statistics, make sure they are the latest statistics publicly available.