pci express 3.0 x16 slots

1 x PCI Express x16 slot, supporting PCIe 3.0 and running at x1 (PCIEX1_4) 2 x PCI Express x1 slots, supporting PCIe 3.0 and running at x1 (PCIEX1_2, PCIEX1_3)

1 x PCI Express x16 slot, running at x16 (The PCI Express x16 slot conforms to PCI Express 3.0 standard.).

Hi,Can someone explain to me concisely as possible what this mean: PCI Express 3.0 x16 (x4 electrically) card slot (slot 1) and what is the difference between it and that: PCI Express 3.0 x16...