What is Intel 955X chipsets

[SpringNite]

Hello guys, i know that those motherboards got a chipset that write in Nvidia or ATI or Intel xxxX chipsets. And my question is What is the chipset that named Intel975X Express chipset or wat Intel 9xxX Chipset.

And what is the different between Express chipset or chipset ?

 

[SpringNite]

Is it express chipset is only for PCI express Or SLI ?