It is a terminal multiplexer. You will be able to find youtube videos. The gp is talking about a tool called gnu screen. If you need a more distinct token to search on try “tmux”.

On which, see: <https://news.ycombinator.com/item?id=44787374>

Pretty sure they mean GNU screen, a terminal multiplexer. Similar in functionality to tmux or zellj (a newer alternative) if you have heard of those.