DDR stands for Double Date Rate, and that means it doubles the bandwidth of the memory by transferring data twice as fast on both the rising and falling of the clock cycle. 

CAS stands for Column Access Select or Column Access Strobe, and that essentially means the number of cycles for the memory to get information and then process that information. Also keep in mind that a lower CAS is much better than a higher CAS, so try and keep CAS as low as possible when overclocking. 

This memory is also Dual Channel which means better overall memory bandwidth resulting in superior performance. In order to benefit from this technology, you will need to have a dual channel motherboard. Non-dual channel motherboards do not have two fully independent 64-bit memory controllers, but dual channel boards do, which means they have a 128-bit memory interface. Now they can be installed singly, but obviously performance will be much less at the same MHz.

Detailed Specifications:
- Available in 512MB (2X256MB) & 1GB (2X512MB) Dual Channel DDR Kits
- 184pin, Non-ECC, Un-buffered, high performance DDR memory modules
- GeIL 3.5ns 32x8 Density DDR Chip
- 6 Layers Ultra Low Noises Shielded PCB with Gold 30u" Plating
- Optimized SPD for Intel 875/865 chipset Dual Channel DDR motherboards
- Platinum Copper Heat Spreader
- Lifetime Warranty
- CAS 2.5 4-4-7 @ DDR500MHz PC4000
- 2.6V-3.1V