typedef is useful in a lot of situations.
Basically it allows you to create an alias for a type. When/if you have to change the type, the rest of the code could be unchanged (this depends on the code, of course).For example let's say you want to iter on a c++ vector
vector<int> v;...for(vector<int>::const_iterator i = v->begin(); i != v.end(); i++) {// Stuff here}In the future you may think to change the vector with a list, because the type of operations you have to do on it. Without typedef you have to change ALL occurrences of vector within your code.But if you write something like this:
typedef vector<int> my_vect;my_vect v;...for(my_vect::const_iterator i = v->begin(); i != v.end(); i++) {// Stuff here}Now you just have to change one row of code (i.e from "typedef vector<int> my_vect" to "typedef list<int> my_vect") and everything works.
typedef also saves you time when you have complex data structures which are very long to write (and difficult to read)