overload new and delete

Why do one need to overload operators like new and delete. And also curious to know, why do people overload ‘[]’ operator?

Please let me know..

Thanks

new and delete are overloaded in case someone wanted to redefine the way memory was allocated. operator[] is overloaded for bounded arrays like a std::vector:

std::vector<int> a;
a.push_back(3);
std::cout << a[0] << std::endl; //prints out 3

You should be able to overload as many operators as possible so you have the flexibility to define them the way you want them to operate on your class.