Health nurse is a nurse trained specifically in mental health
A community mental health nurse is a nurse trained specifically in mental health (not usually all the physical stuff too!). He or she will help you with support and advice for what ever mental health problem you may have, they vary in what they can do, some are trained in specific therapeutic techniques like cognitive behaviour therapy, Some are great all rounders who offer support and advice about your particular problems and may help you will some practical things too like anxiety issues or benefit forms, or medication. Here are some useful abbrieviations
CMHT - Community mental health team
CPN - Community Psychiatric nurse
RMO - Responsible medical officer (usually your psychiatrist)
RMN - Registered mental health nurse, the qualification the nurse needs whether they work in a hospital or in community.
CSW - Community support worker (an unqualified but experienced worker in mental health - can help with shopping and appointments and support as needed)
SW - Social worker (If you have more complicated issues about housing,bills, financial worries and debts)
OT - Occupational therapist (helps you build up skills again like cooking and budgeting, also does stuff like anxiety management and relaxation - not a nurse)
Oh by the way a CPN usually visits about once a fortnight but can be a bit more if needed or every four weeks if you don’t need so much. Hope this helps.