I have a Win10 DeskTop Dell System.

I have the XPS 8930 System and they Tell Me one of My SATA Ports on My MotherBoard is a S.A.T.A 3. PCIE Interface.

What is this Type of Interface or am I not Understanding what they Told Me?

 

SATA3 is a disk interface specification. All SATA disks will work on that, as it is backwards compatible with SATA 2 and SATA 1.
PCIE is usually a slot specification for things like video cards or other add-on cards. There is PCIE-16 and -8 and -4 and -1 slots, all different sizes.
Finally, there is a M.2 card slot for SSD (SATA or PCIe/NVMe). This is for some types of SSD devices which come as "SSD" or as "NVMe/PCI" types. The M.2 will "usually" operate with either type. The NVMe is faster as the M.2 interface runs as though it was a PCIE slot.

 

So it will Look just like a SATA Interface but You can Plug In the M2. Card and the M2. Card will let You Plug PCIE Cards into the M2. Card Right?