Of course, the meanings of 'low' and 'high' frequencies are relative.
The simplest high-pass filter consists of a capacitor in series with the signal path in conjunction with a resistor in parallel with the signal path. The resistance times the capacitance (R×C) is the time constant; its reciprocal is the cutoff frequency, at which the output voltage is 70.7% of the input.
Such a circuit would be used in combination with a Tweeter, Loudspeaker.