Primary: A job in which produces a product. These jobs are very labor intensive, as well as little pay, these jobs are in least demand. (but were very popular 100 years ago) An example of this job would be: lumberjack, mining, etc.
Secondary: These jobs are in which they process a product. these pay a little better than primary, and are a relatively safer environment. (these jobs have remained the same popularity as they have had about 100 years ago) these would be factories, that process a product. An example is, processing ore, (in a factory)
Tertiary: These jobs have the most pay, they are the most popular among people today, they have the least amount of labor involved, as well they usually have good benefits and pentions. These jobs are everywhere, they provide the customer with the product, doctor, lawyer, store owner, etc, etc, etc.
grade nine geography, i knew i listened/studied for a reason lol