Where [source] could be WEB-DL or HDTV and [group] might be something like AVS or KILLERS .

If you need to find a matching release, typical scene or P2P groups would name something like:

Young.Sheldon.S04E18.XviD.[source]-[group]

It seems you're looking for a specific for a video release of Young Sheldon Season 4, Episode 18.