What is the difference between PCIe Gen 3 and PCIe Gen 4?

What is the difference between PCIe Gen 3 and PCIe Gen 4? pcie 4 slot By you sticking a UAD-2 card into the second slot, the motherboard detects this and automatically throttles the first slot down to 8x assuming you have stuck in pcie slot cover PCIe bifurcation PCI Express bifurcated Riser Card ITX to ATX x4x4x4x4

pcie 4 in pcie 3 slot As PCIe slots can be configured with one lane or multiples of four For example, PCIe x8 refers to a Gen 4 expansion cardslot with 8-lane