Run this wizard and it will tell you which memory your computer uses.
Crucial Memory Advisor Toolhttp://www.crucial.com/index.asp
You can also download Everest and it will tell you all about your computer.http://www.lavalys.hu/products/download.php?pid=1&lang=en
Basiclly he is right:
SDRAM = Synchronous DRAM
DRAM = dynamic random access memory
SODIMM = Small Outline DIMM (commonly in notebook computers)
DIMM = dual in-line memory module
SIMM = Single in-line memory module
You also want to make sure to get the correct Pin & Speed.