Definition listed here for "Ground" symbol.
2021 SOLIDWORKS Help - View Mates and View Mate Errors Windows
FYI for anyone, the second one has the "Lock Rotation" option selected.
If you're referring to one with the solid circle and the other one, then as Jeff Parker said, it indicates that rotation is locked for one and not the other.
If you're referring to the arrow, then as Matt Lombard indicates it's supposed to indicate a Mate that locks this component in place, as opposed to a mate that locks other components in place related to this component. I have not found this symbol to be accurate.
Hello,
Some screen shots for what's posted above.
The circles without the centered dot indicate a concentric only mate.
But a concentric mate has the option to lock rotation:
When you do lock rotation, the centered dot is displayed to indicate this:
There are other ways to lock rotation, but when done within the concentric mate, the dot indicates the lock state.
Kevin
The one with the arrow is a concentric that leads to ground. Meaning that concentric helps fix all the degrees of freedom of that part.