DDR2 (Double Data Rate 2) SDRAM is a type of computer memory that was widely used in desktop and laptop computers. 

It operates at a lower voltage (1.8V) compared to its predecessor, DDR1, which helps reduce power consumption. 

DDR2 memory modules have a specific pin configuration that makes them physically incompatible with DDR1 or DDR3 slots. 

It supports dual-channel architecture, which allows for simultaneous data transfer on two memory channels to improve system performance. 

DDR2 has a prefetch buffer of 4 bits, which is double that of DDR1.