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#10
The standoffs look like little pegs that have a screw on the bottom and screwhole in the top. They keep the motherboard raised off the case. In your pics you dont need standoffs because each post for the screws are already raised.
I think for any case that fits multiple form factors (like mATX and ATX) have holes for both and you put the standoffs in the holes that line up for your Motherboard.
Just thought I would mention it in case someone building a computer is confused. As I was when I had to install standoffs.
Another thing to mention would be the front panel connectors as this goes from the case to the motherboard. It is different depending on what the front panel has, but sometimes the included instructions are vague.
Edit: Thanks Sergio