Note that it is $15k ($14k last I checked, but it may have risen) per gifter-giftee pair.

So I can give my son $14k, my wife can give my son $14k, and we can both given my daughter a combined $28k all without even registering against the $5 million lifetime exclusion or paying any gift taxes. And couples can do that every single year for decades, which adds up to millions even without touching the exclusion.