Is a professional fee an income?

Excuse me, could you please clarify something for me? I've been reading about different types of income and came across the term 'professional fee.' I'm a bit confused about whether a professional fee can be considered as a form of income. Is it a type of compensation that professionals, like doctors, lawyers, or accountants, receive for their services? And if so, does it fall under a specific category of income, such as earned income or passive income? I'd appreciate your insight on this matter.