An Information filtering system is a system that takes out unwanted or redundant information from an information stream using (semi)automated or computerized methods previous to presentation to a human user. Its major goal is the management of the information overload and increase of the semantic signal-to-noise ratio. To do this the user’s profile is compared to some reference characteristics. This distinctiveness may start off from the information item (the content – based approach) or the user's social environment (the collaborative filtering approach).
While in information transmission signal processing filters are employed against syntax-disrupting noise on the bit-level, the methods used in information filtering act on the semantic level.