What are PCIe x1 Slots Used For?

PCI vs PCIe Slot · PCI-E x16 slot: It is 89mm long and has 164 pins It is often used for graphics cards and backward compatible with x1 x4

I see various mobos with, for example, 'half-length' PCIe x16 slots But this is a contradiction in terms A PCIe x16 slot by definition is

pcie4 slot PCIe slots come in different sizes, with the most common being PCIe x1, PCIe x4, PCIe x8, and PCIe x16, which indicate the number of lanes

pcie 50 slot Typically, the size of the PCIe slots also represents the number of PCIe lanes For instance, PCIe x16 slots have x16 PCIe lanes, and PCIe x1