The provinces of Sweden are historical and cultural regions. Today, they no longer have any administrative function, but still serve as a basis of cultural identification.
The provinces do not have officially approved flags, but still flags have been created for some provinces and are in unofficial use.
The provinces do have coat of arms, and sometimes they are made into flags:
Jämtland does not want to play with the other boring kids anyway. They consider themselves an independent republic standing above puny provincial flags. Because the flag was created for the Republic Jamtland, it looks different than all other provincial flags.