What is the difference?

Chris is correct, but just to add on to his answer:

Salomon has to my knowledge stopped making Snowblades. I believe they have been off the market for about 3-4 years, although some still can be found being sold as "new". LIne was producing ski boards as well for several years, but I couldn't find any in their product line-up for 2008-09.

There is also the Snow Skate and frequently this product is confused with Snowblades or ski boards. The Snow Skate is essentially a skateboard sized snowboard and several ski areas have a dedicated area for their use. Most do not have edges or a binding that would allow them to be used on regular trails.

It's about the same difference between in-line skates and Rollerblades.

Same things - one's a general name, the other is a specific brand.

Ski boards are what most manufacturers of the really short skis call them.

Snowblades are ski boards that Salomon used to make or might still make.

about 120cm