DDR2 desktop memory (Double Data Rate 2) is a type of RAM that succeeded DDR memory, offering faster data transfer rates and improved performance. It operates at lower voltage (1.8V) compared to DDR (2.5V), which helps reduce power consumption and heat generation. DDR2 uses a 240-pin DIMM interface and is not backward or forward compatible with DDR or DDR3 due to different keying and electrical requirements. It features higher clock speeds, typically ranging from 400 MHz to 1066 MHz, and improved signal integrity through on-die termination. Primarily used in desktop computers from the mid-2000s, DDR2 provided a reliable and cost-effective solution for multitasking and running demanding applications at the time.