Can a PCIe Device Work in a PCIe Slot?

Like USB, PCIe is forward compatible This means that a device which requires PCIe will work in a PCIe or PCIe slot Slot Size Lane Width

What is the point of even buying a video card that uses PCIe if people have motherboards that only have PCIe slots?

pcie slot x16 PCIe x16 Slots 1 2 3 4 7 5 AMD B550 Ryzen AM4 Gaming ATX motherboard with PCIe® , teamed power stages, Intel®

pcie expansion slot The first one is 16x electrically, but this will automatically drop down to 8x if a card is installed in the second slot The second slot is 8x electrically