The State I reside in has many counties and each has its own definition of what role the PHN will play in their community--Some have nurses working in many aspects of community nursing (several already mentioned) and others have specialized programs--Homeless, TB, Maternal-Child, CPS-Fostercare, Adult Services, CD, Clinics, etc.
PHN work can be rewarding--but just like any work sites, there are downsides--for example, gov't work operates at a slower rate, the wage tends to be a little less than the hospital setting, harder to get rid of bad supervisors, creativity can be stiffled b/c it is tax payer based, higher education is often not reimbursed, nor higher wages for advanced certs, programs are at the whim of public opinion,
Having said this, the role is worth all of the above. Often, the public is greatful for your help.