The notioii of relevance isone of the evaluation methods of information retrieval. The better weunderstand the meaning of relevancefrom different points of view, thebetter we can increase the effectiveness of information systems. Besidestechnology, the individual differenceof human cognitive decisions is themost important factor that influencesthe information retrieval. This articlediscusses the background of TefkoSaracevic and his major publicationson relevance and on informationseeking and retrieving behavior. Theconclusion may be helpful to designthe searching interfaces.