Basically it means that if you collect both
a) public material information and
b) nonpublic nonmaterial information
and by combining it you get a conclusion that is of nonpublic material nature, then you are not in violation if you use it in your investment actions.
Can’t remember the exact definition - I think it’s defined either in SS1/2 or in the Handbook. Material means that the information affects the value of an investment or that an investor would want that information before making an investment.
So, for example it’s material to know that a company reduces its projected earnings by 10%.