What is the difference between Formal Parameter and Default Arguments?

Question

I have seen at many places that object is passed as reference and as constant reference.
I want to know the usage of each one.

Answer 1

Argument is often used in the sense of "actual argument" vs. "formal parameter".

The formal parameter is what's given in the function declaration/definition/prototype, the actual argument is what's passed when calling the function, an instance of a formal parameter, if you will.

That being said, they're often used interchangably, or depending on language/community, and I've also heard "actual parameter" &c.

So here, x and y would be formal parameters:

return_type fun_name(type x, type y) {
...
}
Whereas here, in the function call, 5 and z are the actual arguments:

fun_name(5, z);