Quadband handsets support four network bandwidths, whereas the triband handsets available today support only three bandwidths.
There more bandwidths a handset supports, the higher the chance that your handset will work in about any GSM network worldwide.
Triband handsets typically allow your handset to be used in Europe and in the US. I assume quandband handsets are usable in Europe, US, and Asia.
This was first published in March 2002