I m confused about types of AMD motherboards and Expansion Slots of it?

The numbers 890FX, 890GX etc are the Chip Sets With 890FX being the latest and you have them in the correct declining order. they are the bios controllers and recognize the items like USB 3.0 and SATA 6GT/s the 890, 880, 875 will recognize the 6 core AMD. the older ones (790) will not. When buying a new mother board its best to get one with the newest "chip set" (890FX) to insure some future proofing. the PCIe (ver. 1.1, 2.0, 2.1 and the soon to be announced 3.0) X16 slots are designed for the video card. ALL are compatible with the PCIe X16 slot regardless of the version. There is a PCIe x4 slot available on some boards and i did see a very few video cards made for it...however they run on the same bandwidth as the X16 slot so if used it would take away bandwidth from the x16 video card.