Very simply, a board of nursing regulates nursing practice while a professional nursing organization advocates for nurses.
Let's start with a board of nursing. We have state boards and also a national board of nursing in the US, named the National Council of State Boards of Nursing (NCSBN). State boards regulate nursing practice by developing uniform rules and regulations for the field, accepting/accrediting nursing programs, overseeing the nursing licensure training process and enforcing the law regarding nursing practice. The NCLEX-RN and NCLEX-PN exams are developed and administered by the NCSBN. The state boards work together with the NCSBN to protect and advocate for the safety and well-being of all patients. The NCSBN provides free training resources on their website. There are video libraries that discuss nursing regulations, substance abuse in nursing, professional boundaries in nursing and social media guidelines for nurses. There are also free and paid classes for the NCLEX-RN and NCLEX-PN exams online.
Nursing associations can be state-based, national-based (American Nurses Association - ANA) or international-based (International Council of Nurses - ICN - which is a federation of 130 national nurses associations). Nursing associations can be specific, or specialty-focused based on:
1) type of nursing (ambulatory, emergency room, etc.)
2) specific nursing fields (maternal care, cardiology, etc.)
3) age-specific (neonatal, geriatric, etc.)
4) ethnic (black, male, etc.)
5) advanced nursing specialties (nurse attorneys, nurse educators, certified nurse midwives)
6) education-specific (National League of Nursing - NLN, American Association of Colleges of Nursing, etc.)
Below are some links that you might find useful. Thanks for the question!