Noob question: why do I need more PCIE x16 slots?

Is PCIe x16 the standardcommon interfaceport on a modern x16 slot PCIe UD Slot X： PCIe x16 slot with 10X strength for graphics card; WIFI EZ-Plug: Quick and easy design for Wi-Fi antenna installation; M x16 slot PCIe x16: The powerhouse slot for top GPUs & demanding hardware Delivers max data transfer speeds

book of oz slot The PCI Express x1 to x16 adapter accommodates low profile x2, x4, x8, x12 or x16 PCI Express cards, eliminating the cost and hassle of upgrading a PCIe card or