RC circuit
This shows that, if the output is taken across the inductor, high frequencies are passed and low frequencies are attenuated (rejected). Thus, the circuit behaves as a "high-pass filter". If, though, the output is taken across the resistor, high frequencies are rejected and low frequencies are passed. In this configuration, the circuit behaves as a "low-pass filter". Compare this with the behaviour of the resistor output in an RC circuit, where the reverse is the case.