What is the difference between a function declaration and a function definition?

Why are default argument specifiers in the declaration but not the definition?

For overloading arithmetic symbols (+ - * /) on Fraction objects, which is better, member functions or non-member global operators?

Explain the difference between pass-by-value and pass-by-reference. Why would you use one instead of the other?

Explain the difference between preprocessor macros and inline functions.