Why was I charged a transfer fee?

Excuse me, could you please explain why I was charged a transfer fee for my cryptocurrency transaction? I understand that there are often fees associated with transactions, but I was hoping to gain a clearer understanding of the specific reasons behind this particular charge. Was it due to the network congestion at the time of the transfer? Or is there a standard fee that is applied to all transactions, regardless of the circumstances? I would greatly appreciate any insight you can provide on this matter.