How to DC bias op amp?
The example they're considering is you have a signal that swings between 1 and 2 V, and you want to scale and offset it to get an output signal that swings between 5 V and 0 V. 

So you could consider the operating point to be when the input is 2 V and the output is 0 V , which they call "(2 V, 0 V)". Then the input signal would always be a negative voltage added to the 2 v operating point.

Or you could consider the operating point to be when the input is 2 V and the output is 5 V, which they call "(1 V, 5 V)". Then the input signal would always be a positive voltage added to the 1 V operating point.

This nomenclature is not common, and you shouldn't worry about ever seeing it again.