This is a voltage follower or buffer amplifier circuit, where the output is simply equal to the input. The advantage of this circuit is that the op-amp can provide current and power gain; the op-amp draws almost no current from the input. It provides low output impedance to any circuit using the output of the follower, meaning that the output will not drop under load. The load is a 1k resistor in this case; the op-amp provides all the current needed to drive the load, without requiring any current from the input.
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