Filter is a device used to eliminate unwanted noise. The input or output is filtered to obtain pure DC power. The filter effectively filters out frequencies at a particular frequency or frequencies outside of that frequency. Its function is to get a specific frequency or eliminate a specific frequency.

Low-pass filter is a component or combination of electronic circuits that allows signals below the cutoff frequency to pass, while signals above the cutoff frequency cannot pass.

Take an example.A solid barrier is a low-pass acoustic filter. When playing music in another room, it is easy to hear the bass of the music, but most of the treble is filtered out. Similarly, a car plays very loud music, while in another car it sounds like a bass beat, because the closed car and air gap act as a low-pass filter, weakening all the treble.