To congratulate someone means to express happiness and approval for their success or good fortune. When you congratulate your friend for winning the spelling bee, you're celebrating their achievement with them. You might say “Congratulations!” or “Great job!” or give them a high five.

Congratulations feel good to give and to receive because they recognize real effort and accomplishment. When your sister gets accepted to the college she wanted, when your teammate scores the winning goal, when your neighbor's new baby arrives, these are all moments for congratulations.

Congratulating someone lets you share in their happiness. You notice what happened and feel genuinely pleased for them.

People congratulate each other for all sorts of things: graduations, birthdays, promotions, victories, new homes, and countless other occasions worth celebrating. The sincerity matters more than the words. A heartfelt “I'm so happy for you” means more than an elaborate speech delivered without genuine feeling.