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 ssd in pcie 3 slot Best budget; 3 Best 2TB+; 4 Best for Steam Deck; 5 Best for PS5; 6 Best PCIe 5; 7 How to spot pcie 40 in pcie 30 slot 3 slots to see if there is any performance difference when switch between slots And, I also

pcie 40 in pcie 30 slot It is possible to expand with up to three NVMe SSDs, with each slot supporting a maximum capacity of 2TB The leftmost slot is PCIe compatible, with a

pcie slot function 2 x16 Gen 4 Card uses PCIe , which doubles the bandwidth per lane compared to PCIe With four slots, it offers up to 256 Gbps of bandwidth per card, ssd in that slot is a PCIe x2 nvme You can GPU: GTX 1660 Ti, X570 based motherboard