What is PCI Express? Do PCIe lanes, slots, and versions matter?

Introduction to PCI Express - What is PCIe Bus? pcie slot size Generally speaking, there are five physical sizes of PCIe cards: x1, x4, x8, x16, and x32 (FYI, PCIe x32 does exist with a maximum of 32 lanes, pcie x1 in x16 slot PC Talk Forum I see various mobos with, for example, 'half-length' PCIe x16 slots But this is a contradiction in terms A PCIe x16 slot by

pciex16 slot For example, if you connect a PCIe expansion card to a PCIe slot, the card will perform to the PCIe specs PCIe Gen 4 offers