M321R2GA3EB0-CWM is a Samsung ddr5 rdimm.
A DDR5 registered DIMM carries buffered memory modules for servers, with on-module power management.
It is used in servers and data centre systems, where the part has to hold its specification over the life of the equipment.
Within the family, this ordering code is the one specified for 5,600 Mbps per data pin (equivalent MT/s) data rate.
The closest other ordering code is M321R4GA3EB0-CWM, which differs in capacity (32 GB against 16 GB).
The data sheet fixes the memory technology at DDR5 SDRAM.
Its advantage is that the specification is published and stable, so the design does not depend on bench characterisation.