Filters are so named according to the frequency range of signals that they allow to pass through them, while blocking the rest. The most commonly used filter designs are as follows:
The Low Pass Filter – the low pass filter only allows low frequency signals from 0Hz to its cut-off frequency while blocking those any higher. The exact frequency response of the filter depends on the filter design.
The High Pass Filter – the high pass filter only allows high frequency signals from its cut-off frequency and higher to infinity to pass through while blocking those any lower. Still, the amount of attenuation for each frequency depends on the filter design.
The Band Pass Filter – the band pass filter allows signals falling within a certain frequency band setup between two points to pass through while blocking both the lower and higher frequencies either side of this frequency band.