The adapter is a converter to convert the available PCI-E of a motherboard into a USB 3.1 header.
Connector1: USB 2.0 Socket
Connector2: USB 3.1 Front Panel Header
Thus the USB 3.1 port of a housing can also be supplied with USB 3.1 without a suitable mainboard.
USB 3.1 Front Panel Socket USB 2.0 to PCI-E Express Card Adapter for Motherboard