Suspended chords are traditionally used to transition from one chord to another while holding out a suspended note, then resolving the suspended note. An example is an Am chord going to an Esus4 chord to an E chord (then usually back to Am or to C). The A note on the third string in the Am chord gets carried over to the Esus chord, creating some tension that is released when you pick up the A note and play the normal E major chord.

Many songs, however, use the suspended chord as a stand alone chord, which actually makes the chord technically an open 5th or 4th chord. If that's confusing reply to this and I'll try to explain further.

Nick

http://www.toptierguitarstudio.com