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

What is the difference between PCIe Gen 3 and PCIe Gen 4? 16x pcie slot I have 2 x16 pcie and 4 x1 slots I have 2 x8 cards in the x16 slots, but need basic display adapter functionality for debian xfce lucky shot slot PCIe SSD Performance; EZ-Latch：PCIe x16 Slot & Connectors with Quick Release & Screwless Design; Fast Networks： LAN & Wi-Fi 6E

lucky shot slot 1 Solid Pin Power Connector ; 2 DVI ; 3 DisplayPort + HDMI ; 4 Realtek GbE LAN ; 5 Ultra Durable PCIe Slot · PCIe® Slot · Running 1* x16

bacground slot Identifying Different Types of PCIe Slots In ASUS 「PCIe x16 Slots - 4」