* To indicate the end of the song. When someone writes "[Chorus]", it means that the chorus of the song is about to begin. Similarly, when someone writes "[Verse 2]", it means that the second verse of the song is about to begin.
* To help people follow the song structure. When someone writes "[Chorus]", they are making it easier for people to sing along or play along with the song. By providing these cues, people know when to come in and when to stop.
* To add visual interest to the song lyrics. When someone writes "[Chorus]" or "[Verse 2]", it breaks up the text and makes it more visually appealing. This can make it easier for people to read and remember the lyrics.
Additionally, some people use to indicate a change in the musical arrangement of the song, such as a change in tempo or key.