What exactly does the spec “PCIe x16 slot ” mean?

Hyper 2U SYS-221H-TNR PCIe Slot Configuration Options Each expansion card slot is assigned to specific motherboard PCIe x8 MCIO connectors or PCIe x16 slots

PCIe x16: PCI Express is the motherboard slot that a With an eGPU setup we typically compress an x16 slot down to an x1

pciex16 slot configuration * The PCIEX8 slot shares bandwidth with the PCIEX16 slot When the PCIEX8 slot is populated, the PCIEX16 slot will operate at up to x8 mode 1 x PCI Express

ana slot Slot configurations without DWCM​ ; Riser 12, x16x8x8 , x16x16E , Ex16x16, Riser 3 ; Slot 14, PCIe x16, PCIe x16, Empty, Slot 7