At power on, the capacitor (104) is initially discharged and will hold the RESET pin low, then very quickly thereafter, the transistor will begin conducting and charge the capacitor to Vcc (3.3-~0.2volts) and the RESET pin will be held high. If the power should fail momentarily, the C will hold the reset pin high (noting it will start to discharge through the reset pin and the reversed bias transistor junction) and if power returns within a yet to be determined time-constant of the C and some R, the PIC will not have been reset, eventually if power is off for long enough the C will be discharged and the process of power-on reset can resume. It is a form of brown out device as it speeds up the reset transition time during power perturbations.