Why can I create a map with my class without overloading operator

Question

Programming

there is a class

class Item {
private:
  string name;
  int price;
  Category *category;

public:
  Item( ... );
  ~Item();
  //code
};

in the order class I create a map with Items

class Order {
private:
  static int number;
  Customer *const customer;
  map<Item*, int> *items;

public:
  Order( ... );
  ~Order();
  //code
};

in the Order constructor

items = new map<Item*, int>;
  items->insert(std::pair<Item*, int>(item, 1));

Answer 1

because your key is a pointer

Answer 2

Why works map with my class without define operator

Why write English without knowing which one?