sloth_potato :
Paul NZ :
Well if youre not buying an M.2 ssd dont worry about it
what if I am???
I linked the motherboard page and included an image for your convenience above. But since you didn't see it, here it is again.
SinxarKnights :
https://www.asus.com/Motherboards/PRIME-H270-PLUS/specifications/
It is trying to tell you that if you use M.2 SSD, some SATA ports will be disabled if you use SATA mode. You will likely want it in PCIe x4 mode anyway.
So what this means is using a M.2 SSD in the first slot then setting it to SATA mode will cause the first SATA port (where you plug in a normal hard drive or SSD) to be disabled. Meaning it won't do anything if you plug a drive into that port. If you add another M.2 SSD in the second slot then the number 6 SATA port will be disabled, meaning it won't do anything if you plug something into it.
However, if you use modern M.2 SSDs, you will want them in PCIE Mode for max speed. When you do this, all the SATA ports will work normally. It is just a quirk of having limited bandwidth available to share between all devices