What are operator functions in C++?

Answer 1

Operator functions define what exactly operator (like ++ OR += etc) do.
Those are defined at a low level for (basic) datatypes but you can overload them for your own classes.

Answer 2

An example of operator overlaoding: https://code.sololearn.com/c4BgbEv35NSx/#cpp

Implements pre- and post-increment as well as assignment for the class. Should give you the gist of it...