The federal government allows each Canadian province and territory to "nominate" applicants based on the particular economic and labour requirements of the province. As such, the provinces can select individuals who wish to immigrate to Canada based on their eligibility for a specific provincial program, and on the condition that the individual will settle in the respective province.
The PNP programs are another option to immigrate to Canada, especially if you do not have enough points to be selected under Express Entry, or are not eligible for any other federal immigration category. Participating provinces and territories have signed agreements with the Immigration Refugee Citizenship Canada (IRCC) that allow them to select immigrants who meet the requirements that they have set forth. If an individual qualifies for a PNP, the province will nominate them through Express Entry by awarding them 600 additional points as part of the Comprehensive Ranking System (CRS).
Provinces with PNP programs each have their own selection criteria to find immigrants with skills that the province needs which they cannot hire locally. The selection criteria and occupations vary across provinces, from information technology, medicine, agriculture, trades, business, investors, and people who have ties to Canada.