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

My MSI RTX 3060 Gaming X has been detected by my system pcie x 16 slot PCIe x16 to two PCIe x16 Slots Expansion Docking Board Allows the upstream host to turn on the downstream sub-system's power For auto-switch you pcie x4 in x16 slot Specifications x 1

pcie slot qrelease It's a slot of x16 size but electrically x4 This