SDRAM is actually SDR SDRAM, and DDR is actually DDR SDRAM, though the former does not usually have the SDR in front of it. The letters SDR and DDR stand for Single Data Rate and Double Data Rate, and the letters SDRAM stand for Synchronous Dynamic Random Access Memory. There are a lot of little differences, except the voltage they use are different,the main one that affects the user is speed:

DDR can transfer data at roughly twice the speed of SDR.
More speedy data rates = better performance.

They are not interchangeable and in general they`re not used at the same time even your MB support both the two type.

DDR3 is the successor to DDR2 and DDR memory technology. DDR3 can break the GHz barrier with ease and is unmatched in bandwidth performances. DDR3 memory modules advantages are ultra fast speed, greater bandwidth, lower power consumption and better heat dissipation capabilities. The original design purpose for DDR3 memory modules were to work coincide with quad-core CPUs for maximum computing performance.

For actual applications, DDR3 is best suited to serve on high end PCs, workstations and servers where massive data processing is required. DDR3 memory module’s Column Write Delay (CWD) can also improve the bus command efficiencies used in servers. Additional bonuses of DDR3 technology is its low power consumption resulting in longer battery life for notebooks and its performance for HD content playback.

FBGA is a smaller package with requires less real estate on the memory module. In other words, more chips can fit onto a shorter module. The greatest benefit of FBGA is that it has less electricalnoise than TSOP chips, which results in improved signal integrity.

Yes and No. Most DDR modules are built with TSOP style chips which have pins sticking outthe sides. DDR chips also come in a less common FBGA package which is physically smaller, anduses a grid of tiny solder balls on bottom to make electrical contact with the board. At present the FBGA package is the standard for all DDR2 chips.

Yes, DDR2 retains the same 64-bit wide data bus used in DDR. Most DDR2 chipsets, like thelatest DDR chipsets, are expected to support dual channel memory, giving an effective 128-bitwide data bus.

CL is short for CAS-Latency where “CAS” stands for “Column Address Strobe” and “Latency” is the time required for a signal to go from A to B. Imagine the memory modules as a data array with Column Address Strobe (CAS) and Row Address Strobe (RAS). For data to enter or exit, the memory module controller must first send an address (column, row) to activate the CAS signal before data transmission. From the time it takes to activate the CAS signal to the signal actually reaching the data bus is refer to as the CAS Latency (CL) value. Therefore, CL2 memory modules are quicker than CL3 memory modules because CL2 requires 2 execution cycles for CAS signal to reach the Data bus and CL3 requires 3 execution cycles. Currently, most common CL values are CL3, CL2.5, CL2 and expect CL1.5 in the near future!!