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

What is the difference between PCIe Gen 3 and PCIe Gen 4? 1 x pcie 3 0 x16 slot connector65; CrossFireX62; 3x 8-pin power connector46; single slot24; low profile18; DirectX 111 Steckplatztyp 16x1; PCIe x161 Kompatibilität Windows 10 1xbet slot What should be: The PCIe spec states that all slots start at 1x and negotiate how many lanes they can use and what clock speed

1xbet slot It's a slot of x16 size but electrically x4 This

1 slot register The PEX1TO16R PCI Express x1 to x16 Slot Extension Adapter allows for PCI Express cards up to x16 in size to be installed into x1 PCIe slots, 1 x PCIe x16 PCIe x16 2 x PCIe x16 1 x PCIe x16 Slots, Multi-GPU, Graphics, Audio, Network, RAID, SATA3, SATA2, SATA Express