A typedef declaration introduces a name that, within its scope, becomes a synonym for the type given by the type-declaration portion of the declaration.
typedef type-declaration synonym;
http://www.digilife.be/quickreferences/quickrefs.htm - STL-Quick Reference (and others)
http://www2.hawaii.edu/~pautler/How-to/c++-compiler-errors.html - Common C++ Errors