Compline is a fancy word that means bedtime prayer. Just like when your parents tuck you into bed and say a prayer, some grown-ups like to do that too before they go to sleep. It's a special quiet time at the end of the day when they talk to God and ask for help with the things that happened during the day or things that might happen in the future. They might also say thank you for good things that happened or for things they have. It's a peaceful way to end the day and feel calm before going to sleep.