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

PCIe x4 SSD on PCIe slots, what would I expect? m 2 4 0 in 3 0 slot Hi, I currently am using a Pi 5 and I have connected via a Blue USB slot an External SSD enclosure, with an PCIe Gen 4 NVMe SSD in it m2 pcie 40 in 30 slot 3 Best 2TB+; 4 Best for Steam Deck; 5 Best for PS5; 6 Best PCIe 5; 7 How to spot the best deals

m2 slot screw As with previous generations, the standard simply doubles the speed that the PCIe slot runs at It now provides about 2GBs per lane