SODIMM
Small outline dual inline memory module. Smaller and thinner than standard DIMMs, SODIMMs are typically used in laptop computers.

FPM
Fast page mode - A feature used to support faster sequential access to DRAM by allowing multiple accesses to the currently open row to be made after supplying the row address just once.

EDO
Extended data out. An asynchronous DRAM operating mode that improves access times compared to fast page mode (FPM) DRAMs

SDRAM
Synchronous dynamic random access memory delivers bursts of data at high speeds using a synchronous interface. Its is actually SDR SDRAM (single data rate SDRAM) but is usually used to referred to as just "SDRAM."

DDR
Double data rate is a type of SDRAM in which data is sent on both the rising and falling edges of clock cycles in a data burst. It is usually referred to as DDR as opposed to DDR SDRAM.