What is the difference between a refrain, a chorus, and a bridge in a song structure?

In a song structure, a refrain is a repeated line or phrase that appears throughout the song, often at the end of each verse. A chorus is a section of the song that is repeated after each verse and typically contains the main theme or message of the song. A bridge is a section that provides contrast to the rest of the song, both musically and lyrically, and usually appears between the chorus and the next verse.