What happens if you declare money at the airport?

Excuse me, could you please elaborate on what exactly happens when one declares money at the airport? I'm particularly interested in the process, the regulations that govern it, and any potential consequences or benefits associated with making such a declaration. Do all countries have similar protocols, or do they vary significantly? Also, are there any specific thresholds or limits that travelers should be aware of before making a declaration? Thank you for your time and clarification.