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

Hyper x16 Gen 4 Card｜Motherboards｜ASUS Global pcie gen 4 in gen 3 slot The Riser from Dell™ fits into the PCI-E slot of your Dell System Riser cards are used to extend a slot for a chip or card in a fully loaded computer pcie nvme slot 7PCIe slots Up to300Wauxiliary power One PCIe x4 gen 3 Apple IO card Four PCIe x8 gen 4 Two single height Two double height Two PCIe x16 gen 4 Double

pcie expansion slot PCIe x4 x8 x16 Slot USB Type C · 1 out of 5 stars 50+ bought in HP EX900 Plus 256GB NVMe SSD