What does the X4 mean in an PCIe Gen X4 NVME drive?

Hyper x16 Gen 4 Card｜Motherboards｜ASUS Global can i use gen 4 ssd on gen 3 slot Just to be clear, you can run a PCIe SSD in a PCIe slot , it just runs at PCIe speeds Which kind of negates the purpose can you put a pcie x4 in a x16 slot Should I Buy a Gen 4 SSD for My Gen 3 Laptop? Nikos Rentas•22K What are PCIe x1 Slots

candy slot machine slot that the drive can go in The B550 motherboard Is a half-length PCI Express x8 Gen 3 card compatible with a PCIe x4 Gen3 slot?