PCIE - mm PCI Express® Gen 3 Edge Card Connector

Can someone explain me the PCI-E slot variations & sizes of pcie slot sizes PCIe Slots · A PCIe slot that supports an FHFL PCIe card is backward compatible with an FHHL or HHHL PCIe card · A PCIe slot that supports a PCIe pcie 4 slot Item 5 is the PCIe slot 5, on Riser 2 and is connected to Processor 1, it supports a full height, full length 8x card The slot width is 16x Item 6 is the PCIe

pcie slot height Card capacity and size · Slot 1: gen 4, up to x16 lanes · Slot 2: gen 4, up to x16 lanes · Slot 3: gen 4, up to x8 lanes