We can copy element from one Map to another map with same Key and values datatypes. If you trying to copy different key or values it will throw error like "Invalid initial type".
Copying data between two maps in apex
// map1
Map <Integer, String> fruitsMap1 = new Map <Integer, String> ();
fruitsMap1 .put(1,'Apple');
fruitsMap1 .put(2,'Banana');
//map2
Map <Integer, String> fruitsMap2 = new Map <Integer, String> (fruitsMap1);