Confused on mobo specs for new build

[boosbear]

So im building a pc for a friend and Im looking at the gigabyte z170--hd3 motherboard and the specs Im looking at here: http://www.tomshardware.com/reviews/gigabyte-z170-hd3-lga-1151-intel-motherboard,4279.html
say there is no digital audio in. Does that mean my friend can't use a mic unless we also buy an audio card or something? And how can the board support crossfire and not sli? Aren't they the same thing? And lastly, what this m.2 business? I dont know much about it other that it being a smaller faster version of SATA, can I use a m.2 drive with this mobo? The specs say "1x PCIe 3.0 x4 / SATA 6Gbps (1x SATA shared)" which I don't understand at all. Isn't sata and pci-e different?
Thank you

 

[Ironsounds]

Hello... 1) a Microphone is an analog input.
2) SLI and Xfire are not the same, Nvidia and AMD tech.
3) a PCIe lanes go to your SATA controllers... you by pass the Sata controller chip for direct PCIe connection, when using m.2 type drive.