basic use of ferrite bead

I want to know about ferrite bead plz give me best website.

 

Ferrite beads are typically used to provide a lossy impedance at high
frequencies, typically to filter high frequency or RF signals, or to
block such signals from low freq or DC circuits. There are many other
uses as well.

Check out:
http://www.fair-rite.com
http://www.fair-rite.com/newfair/faqfer.htm
http://www.steward.com
http://www.steward.com/applications.asp
http://www.palomar-engineers.com/Ferrite_Beads/ferrite_beads.html

(google is your friend)