Image via WikipediaA SODIMM is a 144-pin memory module designed for use in primarily laptops. These transfer data in 64-bit chunks. There is also a 72-pin SODIMM. This module transfers data in 32-bit chunks.
A SIMM (Single-Inline-Memory-Module) is a 72-pin memory module designed for use in desktop computers. These transfer data in 32-bit chunks.
A DIMM (Dual-Inline-Memory-Module) is a 168-pin memory module, also designed for use in desktop computers. These transfer data in 64-bit chunks.
RIMM is a type of memory module that consists of Rambus Dynamic Random Access Memory chips, RDRAM chips, 184 pins. They transfer data in 16-bit chunks at a 1.6 GB bandwidth.
Computer Memory Types and Memory Technology