Can someone tell me whats the difference between PCI express 2.0 x16 and PCI express x16 slots?

and if i got a PCI express x16 slot (on my motherboard) can i put a PCI express 2.0 x16 video card in it?|||Yes, the difference is that 2.0 doubled the bandwidth so x8 on 2.0 is like x16 on 1.0. The performance loss is not noticable and usually 5% at most.|||Yes