Special-purpose districts or special district governments in the United States

Special-purpose districts or special district governments in the United States are independent governmental units that exist separately from, and with substantial administrative and fiscal independence from, general purpose local governments such as county, municipal, and township governments. As defined by the U.S. Census Bureau, the term special district governments excludes school districts.

Special district governments provide specific services that are typically not provided by general-purpose governments. The services they provide range from basic needs such as hospitals, sewerage, and fire protection to smaller necessities such as mosquito abatement and upkeep of cemeteries. Most special districts provide only a single service. In 2007, the U.S. had more than 37,000 special district governments.
[Wikipedia]

I find the information in the article confusing. Perhaps, the reason for this is that here we don't have divisions such as county, school district, etc. I would have written it somewhat like this:

Special-purpose districts or special district governments in the United States are independent governmental units that exist with substantial administrative and fiscal independence as compared to general purpose local governments such as county, municipal, and township governments. As defined by the U.S. Census Bureau, the term special district governments excludes school districts. Does my rewrite work? And I think the counties, municipals, etc., are subsets of special districts.

What does it really mean where it says: Most special districts provide only a single service?

Please help me.