What is the purpose of the PCIe X1 slot

What is the purpose of the PCIe X1 slot pcie 1x slot NVMe PCIe® x4 & PCIe® x2 • 1x PCIe ® Slot 2 2280 • NVMe PCIe x4 and SATA Mode 12 Smart Fan 5 + FAN STOP • 3 Fan pcie gpu slot 1 additional PCI-Express x1 slot is needed

pcie gpu slot ✓ Mini PCIe to 3 PCIe 1x adapter expands 3 PCI express 1x slot via your motherboard with mini PCIe can use 3pcs PCI express card (Sound Card , Network

pcie 4 in pcie 3 slot Design Ready for PCI Express 1* PCIe x4 & 3* PCIe Unlock the latch of the PCIe slot easily when remove the graphics card in the PCIe slot  Expansion slots: 1x PCIe Gen5 x16, 1x PCIe x1, 1x E-Key Video ports: 1x HDMI ; 1x DP ; 1x eDP USB: 2x USB Gen2 Type-C