Normally, if you visit https://example.com/music/ , you might see a pretty webpage with images and play buttons. But with directory listing enabled, you see a plain, often unstyled list of folders and files.
There are several tools and software applications that can help you index your music library: index of flac music link
Remember: If a FLAC link seems too good to be true (like a brand new Taylor Swift album in 24-bit/192kHz on a random Russian server), it is almost certainly a poorly encoded transcode or a trap. Stick to community-vetted indexes, and always verify your frequencies. Normally, if you visit https://example