anyone?

check out Satriani's post on the circle of fifths in the lessons section.

In simplistic terms, If you want to write a song with more than 7 different notes and chords then you need to change keys. The circle of 5ths indicates which keys are most closely related i.e. if you change from the key of C to G  you need to change only one note namely  F which becomes F#. Changing keys in cycles of 5ths is very common in jazz.

The best interactive circle of fifths ive come across on the net can be found here. Its very useful.

http://randscullard.com/CircleOfFifths/

That's very useful jakjak, and thanks for the simplistic explanation Rene. Bookmarked.