There comes a common question from people about what NOC (National occupational classification) is and why this holds such importance while discussing anything related to immigration to Canada. Down below there is a subtle idea given about NOC and its importance.
The National Occupational Classification(NOC)
For example of National Occupational Classification (NOC):

is Canada’s national guide for professions. It provides a hierarchical framework for classification that categorizes the entire spectrum of occupational activities in Canada to collect, analyze and disseminate occupational data for information on the labor market and administration of employment-related programs. For the provision of the labor market and job knowledge, skills development, occupational forecasting, labor supply, and demand research, employment equity, and various other programs and services, occupational information is of vital importance.

An occupation is characterized as a set of workers, sufficiently similar for the purposes of classification in the work carried out to be grouped under a common mark. In essence, a role includes all the activities performed by a single employee to fulfill their duties.

The kind of work done is the fundamental concept of the classification of the NOC. Job titles are generally classified and grouped in terms of the work normally carried out, defined by the roles, duties, qualifications for jobs, and responsibilities associated with each occupation.

Factors such as the produced or used materials, the manufacturing processes and the facilities used, the degree of obligation and sophistication of the work, as well as the goods manufactured and the services rendered, have been taken as measures of the work done when job titles are combined into occupations and occupations into classes

The NOC contains approximately 30,000 work titles grouped into 500-unit classes, divided according to four levels of ability and ten large occupational categories. The unit groups are focused on the similarity of skills, mainly specified by roles and qualifications for jobs. It is also possible to connect unit groups directly to one occupation (such as NOC 3113 – Dentists) or to more than one occupation (such as NOC 2271 – Air pilots, flight engineers, and flying instructors). Each group of units provides a brief overview of their associated occupation(s), lists their key duties and qualifications for jobs, and provides examples of job titles.

The NOC is used on a regular basis by students, employees, employers, career and vocational counselors, education and training agencies to support career and vocational decisions. The classification is often used to facilitate the formulation of policies and the design and administration of programs and the delivery of services.

As part of a joint collaboration between Jobs and Social Development Canada and Statistics Canada, the NOC was created.