[boost] boost::tuples

I have been using the STL for some time now and have been investigating possible use of the boost libraries in future projects. The most useful library I have found so far was the boost::lamda library. I was reading the documentation and experimenting around with the boost::tuples library. The documentation is excellent and very complete and now I understand how to create tuples and maybe use them is some limited way. Thing is, I can't seem to grasp what advantages there are of tuples over structures and classes? Can someone tell me; what are the benefits of tuples over structures or classes? Thanks, Dennis Bingaman