This is a circuit that is known as wien bridge oscillator circuit. The circuit has positive and negative feedback loop. This circuit is work with control by op amp. This is the figure of the circuit. The circuit oscillates at a frequency determined by the RC time constant at frequency and produces a sinusoidal waveform at the output voltage Vout.
In many cases this circuit is used as sine wave generator which is using rail to rail op amp. [Schematic`s diagram source: Advanced Linear Devices, Inc]