PCIe (peripheral component interconnect express) is an interface standard for connecting high-speed components. Every desktop PC motherboard has a number of PCIe slots you can use to add GPUs(aka video cards aka graphics cards), RAID cards, Wi-Fi cards or SSD (solid-state drive) add-on cards. The types of PCIe slots available in your PC will depend on the motherboard you buy.
PCIe slots come in different physical configurations: x1, x4, x8, x16, x32. The number after the x tells you how many lanes (how data travels to and from the PCIe card) that PCIe slot has. A PCIe x1 slot has one lane and can move data at one bit per cycle. A PCIe x2 slot has two lanes and can move data at two bits per cycle (and so on).
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You can insert a PCIe x1 card into a PCIe x16 slot, but that card will receive less bandwidth. Similarly, you can insert a PCIe x8 card into a PCIe x4 slot, but it’ll only work with half the bandwidth compared to if it was in a PCIe x8 slot. Most GPUs require a PCIe x16 slot to operate at their full potential.
