The best I can find is that there are no legal definitions for the terms you highlighted. More specifically as mentioned in the operational information for CIC
There is no definition in the legislation of “become economically established,” leaving the term open to interpretation. There is also no indication of the exact moment when an applicant must become economically established: immediately upon landing or after an initial period of adjustment. However, it is clear, from the way in which the term is used throughout the economic classes, that to become economically established means to join and participate in the labour market in Canada. It is also clear that the selection criteria do not apply to the provincial nominee class in the same way as they apply to federal skilled workers and that it is the overall intention of the legislation and the Federal-Provincial-Territorial agreements to allow the provinces some latitude in their nomination decisions.
But there is another operational bulletin 499 which clarifies it somewhat:
An indicator of the ability to become economically established is the applicant’s intention and ability to enter the labour market in order to fully support him/herself. If the visa officer is not satisfied that the individual intends to enter the labour market, a refusal of the application should be considered. Part-time or casual work which would not generate enough income to fully support the applicant may not meet this requirement.
So if you use this as a guideline for "becoming economically established" you can infer that "positively contributing" implies that you either fill positions necessary to alleviate the labour shortage (if one exists) in the specific field or create positions to be filled in the Province but that would be more for business PNP.