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

For actual usage you should probably use something like this rcKGqG for a 1x to

PCIe video card 250 GB SATA HDD 7200 rpm ; scalable to 2 terabytes 16x DVDRW DDR2-667 MHz ECC memory NVIDA Quadro FX 1500 256 MB PCIe

can i use gen 4 ssd on gen 3 slot Yes you can install a 16x graphic card in 4x slot but it will limit the performance of the card If you are going to spend money on expensive

can you win big on slot machines Both the blue slots are PCIe x16 The difference is that the 2nd PCIe 16x is capable of wiring