To understand 'this' pointer, it is important to know how objects look at functions and data members of a class. Each object gets its own copy of the data member. All access the same function definition as present in the code segment.
Meaning each object gets its own copy of data members and all objects share a single copy of member functions. Then now question is that if only one copy of each member function exists and is used by multiple objects, how are the proper data members are accessed and updated? The compiler supplies an implicit pointer along with the names of the functions as 'this'. The 'this' pointer is passed as a hidden argument to all nonstatic member function calls and is available as a local variable within the body of all nonstatic functions. 'this' pointer is a constant pointer that holds the memory address of the current object. 'this' pointer is not available in static member functions as static member functions can be called without any object (with class name). For class X, the type of this pointer is 'X* const'. Also, if a member function of X is declared as const, then the type of 'this' pointer is 'const X *const'.