Intel Robson is the NAND flash memory caching technology for notebooks, whereas SnowGrass is the desktop version.
Interestingly, Intel also mentioned that Robson will have a version for desktop computers called Snowgrass. The technology is currently in the works and is planned to be released after Robson. Motherboard makers will have designs that contain a slot designed to take a Snowgrass NAND module. This opens the door for users to customize their motherboards with various sizes of modules for whatever purposes they choose, and also allows the ability to upgrade NAND as it gets less and less expensive. Remember when L2 cache used to sit on the motherboard?
The current specification calls for a modular design but motherboard makers have the option to integrate the technology directly on the motherboard. More info over at DailyTech.