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

slot locations for the PCIe Gen3 IO expansion drawer with two fanout modules Slot Location code Slot 1 P1-C1 Description PCIe3, x16 Slot 2 P1-C2 PCIe3

Product Overview · This PCIe x1 to PCIe x16 Slot Extension adapter provides enhanced compatibility between motherboards and a variety of PCI-Express expansion

x16 slot The number of lanes that a PCIe device supports is typically expressed like “x4” for 4 lanes, “x8” for 8 lanes, and so on x1, x2, x4, x8, x16 PCIe Gen 3

where is slot canyon AMD B550 Ultra Durable Motherboard with Digital VRM Solution, PCIe x16 Slot Ultra Durable™ PCIe Ready x16 Slot; Dual Ultra-Fast NVMe PCIe