In Linux system, what the purpose of "lost+found" directory?

In Linux system, what the purpose of "lost+found" directory?

• Folder for files that have not been closed properly, due to many reasons
• Special folder for old system logs
• Special folder for music
• Folder for deleted system users 

 EXPLANATION

The lost+found folder is a part of Linux, macOS, and other UNIX-like operating systems. Each file system—that is, each partition—has its own lost+found directory. You’ll find recovered bits of corrupted files here...

SOURCE

https://www.howtogeek.com/282374/what-is-the-lostfound-folder-on-linux-and-macos/