Which services can be classified as professional services?

Could you elaborate on what services could potentially be considered as professional services in the realm of cryptocurrency and finance? Are these services typically rendered by individuals or organizations that hold specialized knowledge or expertise in the field? Are there any specific examples of such services, perhaps related to investment advising, tax consulting, or perhaps even security audits and risk assessments? I'm interested in understanding how these services differ from general financial services and how they can benefit those involved in the cryptocurrency and finance industries.