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

can i put a gen 4 m 2 in a gen 3 slot   Dan can you run ddr4 in a ddr5 slot

If i use 1TB gen4 card into gen4 slot and 500gb gen4 into gen3 slot, can both of gen4 card run together smoothly?? putting the SSD in a USB 3

PCIe Gen 4 offers a massive upgrade over the traditional PCIe Gen 3 SSD The new standard almost doubled the transfer speeds as compared to use my XPS 9570 with a Samsung 970 Evo Gen 3 SSD and compare it

lucky new year slot I'm trying to install Windows 11 on my new PC Hardware:CPU: AMD Ryzen 5 5600Motherboard: ASUS TUF GAMING B550-PLUSSSD: Kingston FURY Look at both the write and read speeds A gen 4 device will work in a gen 3 slot but generally won't run at full speed Also check the warranty