Hp z640 NVMe PCIe Crucial card on PCIe expansion car

What is the difference between PCIe Gen 3 and PCIe Gen 4? pcie 4 m 2 in pcie 3 slot obviously, a pcie 4 NVMe drive will get maximum performance in a pcie 4 slot, but I'm trying to get a sense of how the latest drives pcie 4 ssd in pcie 3 slot PCIe Gen 3 operates at 8 GTs which roughly translates to 1 GBs per PCIe lane By comparison, PCIe Gen 4 operates at 16 GTs, or

pcie 30 in 40 slot PCIe doubles the throughput rate per lane, giving users a transfer rate of up to 64GBs Why does this matter? The faster the throughput