What is the difference between RX and RXD?

Excuse me, but I'm a bit confused about the terminology here. Could you please clarify the difference between RX and RXD in the context of cryptocurrency and finance? I understand they're related to some form of communication or data transfer, but I'm not entirely sure how they apply specifically to our field. Are they terms used in blockchain technology, or do they relate to another aspect of the industry? It would be greatly appreciated if you could provide a concise yet detailed explanation to help me understand their significance.