What does PCIe-x16 really mean and how many do I need?

Primary riser cage connector, connected to processor 1 or the southbridge PCIe 3-slot riser cage* PCIe 2-slot x16 riser cage 1

Two types of PCIe slot on an Asus H81M-K motherboard Various slots on a computer motherboard, from top to bottom: PCI Express x4; PCI Express x16; PCI Express

pcie 3 slot slot only supports PCIe x16 which comes from the Z590 chip Is there a problem with the first PCIe slot on this new motherboard?

pcie 40 in 30 slot Distinguished Actually, if the end of the X1 slot is open then it will probably work All the pins of the x1