Yes a mini pcie connector.
So actually the Wikipedia page you linked explains the connector holds pci-express,
sata and USB 2.0 lines. But they also point out the m-sata uses the same
connector. Actually m-sata is electrically compatible (as they point out m-sata drives work in
older Thinkpad wwan slot - which is designed for pci-express cellular modem cards.)
Mini pcie: could have pci-express only lines
Or only Sata lines
Or it has both and maybe also USB 2.0
(I guess it is possible to be USB only but I haven't heard of one)
There is no way to tell. You have to hope your machines documentation has the info.
The case of this machine (Samsung Chromebox) there is nothing in documentation
about the connector. And all I could find on the interwebs were reports of msata not working
in the slot. So I had a good chance of finding pci-express exposed in the connector.
And now they have replicated this genius in the M.2 connector. How do you figure out
which SSD to get? There is keying on the connector but the key for SATA also has 2
pci-e lanes. So a 2 lane NVME drive looks the same as a SATA SSD. Argh!
Thomas