PCI in ga-b75m-d3h mother board

[termite]

This is the spec of my mobo(gigabyte ga-b75m-d3h rev1.1) -
PCIe x16 Slots, Generation:
A) 1, Running at x4 (PCIE4)
B) 1, Running at x16 (PCIE16)

what is the difference? Is A = PCIe 2.0 x16 and B = PCIe 3.0 x16? Can someone please explain...

Thanks!

 

[rgd1101]

http://www.gigabyte.com/products/product-page.aspx?pid=4315#sp

 

[termite]

I saw that. But what does "2.1 x PCI Express x16 slot, running at x4 (PCIEX4)" actually mean? PCIe 2.0 x16 or PCIe 2.0 x4?

 

[rgd1101]

it running at x4 speed and it pcie 2.0