While the exact content depends on what the creator packed, "RP8" often refers to:

The file is the first volume of a split (multi-part) RAR archive . To access its contents, you need to "put it together" with the other parts (e.g., RP8.part2.rar , RP8.part3.rar ) that belong to the set. What is likely inside?

: A popular UX/UI wireframing and prototyping tool . The archive likely contains the software installer or a specific project file (ending in .rp ).