What is professional fee reimbursement?

Could you please explain what professional fee reimbursement entails? I'm curious to understand the concept and how it applies in various industries, particularly in the realm of cryptocurrency and finance. Is it a common practice for professionals in this field to be reimbursed for certain expenses related to their work? If so, what types of expenses are typically covered, and what are the procedures for seeking reimbursement? Additionally, are there any specific regulations or guidelines that govern professional fee reimbursement in the cryptocurrency and finance sector?