What are the different types of plumbing?

I'm interested in become a plumber, I understand I need to complete a 4 year apprenticeship and the journey man's exam.

Manufacturers Representative

There are many different types of plumbing jobs available in each specialization.
Many plumbing jobs are held by pipe layers and pipe fitters
General plumbers are often self-employed workers who maintain commercial and residential pipes, fixtures, and appliances.
To obtain plumbing jobs in any specialization, people must usually receive training at community colleges or vocational schools, complete formal apprenticeships, or both.
Plumbing and heating