what is a pcie x1 slot good for?

Will PCIe x1 x4 cards work in x16 slot? x1 pcie slot 2 x PCI Express x1 slots 2 x PCI slots At the Moment there are 1 x The third PCIE slot will run at only 1x if the second slot is occupied x1 slot List of Motherboards with 3 PCI-Express x1 Slots: MSI PRO Z790-S WiFi, ASRock Z790 PG LIGHTNING, ASRock Z790 PG LightningD4, MSI PRO B660-A DDR4,

x16pciexp slot The width of a PCIe connector is mm, while the height is mm, and the length is variable The 'minor' half of the connector is mm