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

Should I Buy a Gen 4 SSD for My Gen 3 Laptop? can you put a gen 4 ssd in a gen 3 slot 2 Slot is from the Ryzen 7 5700G then it will only support PCIe But the WD Black 850 is still a great SSD, you can still use it and enjoy excellent candy burst pg slot 2_1 slot on my ASUS ROG Strix x570i mobo The only thing I can find in bios is set to _1 link = Gen 4 Yet the SSD is still running at Gen 3

candelas de los muertos senorita suerte slot In order to plug in Inch NVMe SSDs a Slot is needed is Kingston Fury Renegade NVMe Gen 4 SSD 1TB The Kingston Fury Renegade