What is the meaning of a const at end of a member function?
What exactly does the const keyword in C++ mean when it's written at the end of a member function (after the argument list)?
It means that *this is const inside that member function, i.e. it doesn't alter the object.
The keyword this is a prvalue expression whose value is the address of the object for which the function is called. The type of this in a member function of a class X is X*. If the member function is declared const, the type of this is const X*. [section 9.3.2 §1]
In a const member function, the object for which the function is called is accessed through a const access path; therefore, a const member function shall not modify the object and its non-static data members. [section 9.3.2 §2]