PCIe vs PCIe : What's the difference?

PCIe 4 vs PCIe 3: Do you need Gen 4 in 2020? pcie 4 in pcie 3 slot ssd Does anyone know if you can buy a PCIe x16 low profile card that supports FOUR M2 NVMe drives? I found this Supermicro card which pciex16 slot configuration Your PCIe card will run at the lowest generation present So if you put a PCIe card in a PCIe slot, you'll get PCIe performance

pcie x1 in x16 slot  An 2280 solid-state drive , 22 mm wide and 80 mm long Connects to, Motherboard via one of: PCIe ×4; PCIe ×4; PCIe ×4; Serial ATA