Assume the input changes from 0V to +1V instantly. The op-amp will instantly have an imbalance on it's inputs and this "forces" the op-amp's output in a negative direction. Some short time later, the op-amp output will attain a level of -1V and this will totally counteract the initial imbalance caused by the input rising to +1V.
Here it will sit in a kind of equilibrium.
What should be noted is that the op-amp (in this type of circuit) will always try and maintain the voltage difference between it's two input pins as 0. This is the effect of negative feedback and the fact that in this simple analysis, the op-amp gain can be assumed to be infinite.
I also said "some short time later" in the first paragraph and this was to try and illustrate the reactionary mechanism of negative feedback. It does take a finite length of time to deal with instant changes and although in all other considerations I've assumed a perfect op-amp, in this area I have not.