What is this Header on my Motherboard?

[tomworthington2004.tw]

Here is the picture:

https://imgur.com/a/qhFS0

What is it? Is it a USB 3.0 header (like it says)? If so, what cable goes into it? Or is it a PCI-E x1?

 

[MusenMouse]

It does look like a PCI-E x 1 slot. If this picture comes from a propritary system like Dell, HP, Lenovo, etc., the port could be marked for an extra media card reader or a USB hub that attaches to the front of the case.