What is the AUM fee?

Excuse me, could you please explain what the AUM fee is and how it works within the realm of cryptocurrency and finance? I understand it stands for Assets Under Management, but I'm not quite clear on how it's calculated or what it entails for investors. Is it a fee charged by fund managers or custodians? How does it impact the overall return on investment, and are there any factors that can influence its amount? I'd appreciate a clear and concise breakdown of this fee structure.