Noob question: why do I need more PCIE x16 slots?

Power-Supply Management Solution for PCI Express x16 Graphics x16 slot x16 slot, even if the 6-pin 150W-ATX connector is connected and powered This prevents the card from accepting 12V power solely from the x16 slot 228022110 NVMe SSD slot x1 Memory expansion 1* PCIe x16 slot Wireless

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