Those are totally different things.
The early DIMM form factor that applied to laptops is known as SO-DIMM (Small Outline Dual Inline Memory Module). SO-DIMMs are smaller than standard DIMMs, making them suitable for the compact design of laptops. They typically come in various capacities and speeds, allowing for mobile devices to have efficient and upgradeable memory options.
Form factor allowed for larger DIMM modules..and there a re designed to use ATX power supplies.
SO-DIMM (Small Outline Dual In-Line Memory Module) and MicroDIMM (Micro Dual In-Line Memory Module) are both smaller versions of DIMM memory modules used in laptops and small form factor devices. The main difference is their physical size and pin configuration, with MicroDIMM being smaller and having fewer pins compared to SO-DIMM. Additionally, MicroDIMM is less commonly used and has limited compatibility compared to SO-DIMM.
Small Form Factor committee was created in 1990.
The purpose of the small form factor is to make a desktop computer appear smaller in size. It is a computer form factor which can be used for this purpose.
Computer uses Memory installed on DIMM Slots on Motherboards.Nowadays different versions of DDR RAMs are used (DDR1, DDR2 & DDR3).Laptops use similar memories (DDR1, DDR2 & DDR3) but in small form of DIMM Sockets called Small Outline Dual Inline Memory Modules (SO-DIMM) memories.
Small form factor
EDO RAM:extended data output, 50,60,70ns, usually on a 66mhz bus or less.
Dual line in memory module
A form factor houses the internal of a computer: processor, memory, power supply, etc. It is the shell of the inners. The term small form factor PC relates to the chassis of a computer in a very small form.
depending on the laptop, it could be DDR, DDR2 or DDR3. But the form factor is all the same. Its all SO-DIMM memory
ddr dimm is not compatible with the ddr 2 because of the notches. the different notch positions will keep you form installing it.