DDR5
DDR5 is the current JEDEC memory standard, succeeding DDR4. It is not backward compatible — a DDR5 kit will not fit or work in a DDR4 motherboard.
DDR5 is the fifth generation of double data rate memory, defined by JEDEC, the body that standardises memory specifications. It raised per-module capacity ceilings and base data rates over DDR4, and moved power regulation onto the module itself.
Compatibility is decided by the motherboard, not the CPU alone. DDR4 and DDR5 modules use physically different notches and cannot be swapped — a board supports one or the other, never both in the same slot.
Within DDR5 there is a wide speed range (DDR5-4800 up through DDR5-8000 and beyond). Your motherboard has a maximum supported speed; a faster kit installed on a board that can't run it will simply operate at the board's ceiling.