One can gain a lot of insight into the structure of a network by analzing the eigenvalues and eigenvectors of its adjacency matrix. The connection between spectral parameters and the more combinatorial properties of networks and datasets is a subtle issue, and while many results have been established about this connection, it is still not fully understood. This connection has also led to a number of applications, including the development of link analysis algorithms for Web search.
"Schnell haben die Benutzer allerdings begonnen, die Suchmaschine nicht zur Erschließung des Wissens im Internet, sondern als Index ihrer Wirklichkeit zu gebrauchen."