Fully floating pistons - what are they?

[Raffles]

I just purchased a brand new mk3.5 MX-5, and this is part of the spiel from a website I am looking at:

http://www.autoincar.com/2009-mazda-mx-5-minorchange said:

The crucial 500 rpm increase in the rev limit is enabled by greater precision in the engine, namely: a forged crankshaft (this ensures the required rigidity at high engine speeds), fully floating pistons and newly designed valve springs.

What are 'fully floating pistons'?

[Raffles]

Thanks all for the replies, interesting info.