It's a paid service where you can enter a premium link or torrent link to it and it will generate a direct download link. This is very useful if you visit premium sites like Mega and RapidGator where if you don't have an account, it enforces limits such as:

Slow download speed (e.g. max 1MB per second while downloading)
Maximum number of downloads per hour (e.g. 1 file per 5 hours)
No resume support
Unable to download if file is larger than a certain amount (e.g. no more than 5GB per file allowed for non-premium users)

more on the old site: https://old.reddit.com/r/Piracy/comments/q3vqgv/introduction_to_debrid_services/