This specific episode is a major turning point for the series. It follows the team as they relocate to after a tragic loss. It introduces iconic characters and sets up the Red Hood arc, which is a fan-favorite storyline from the DC comics.

The string you provided is a "release name" that tells a downloader exactly what they are getting: Season 3, Episode 1.

If you are looking to watch this episode legally and in high quality, Where to Watch Officially

This is the name of the "release group" that encoded and uploaded the file. Season 3 Episode 1: "Lazarus"