I don't know but perhaps 110 represents the rear hub spacing / spacing of ends of frame that this axle will suit (in terms of the chainline it will give)... and one labelled 120 will suit a 120mm spacing.
This may well be utter bollocks as hubs have the threading for the cog on the shell, and that's not depedant on what spacing the hub is - i.e. a hub can be respaced.
I don't know but perhaps 110 represents the rear hub spacing / spacing of ends of frame that this axle will suit (in terms of the chainline it will give)... and one labelled 120 will suit a 120mm spacing.
This may well be utter bollocks as hubs have the threading for the cog on the shell, and that's not depedant on what spacing the hub is - i.e. a hub can be respaced.