USB 2.X/USB 3.X/USB 4: Every USB device is built to some version of the USB specification, mainly characterized by how much data they can transfer and how much power they can deliver (or at least, those are the main things you need to care about). Say you plug a USB 3.2 SSD into a USB 3.2 port on your computer, but use a USB 3.0 cable—data will only transfer at USB 3.0 speeds. USB Power Delivery (or USB-PD): If your laptop, tablet, or other device doesn't have enough USB ports, you might be forced to choose between charging or plugging in accessories.