A lab is a place where you can safely do experiments. Some (most?) of us work in IT or a related field, and playing with production equipment is a big no-no. So we build ourselves a “production” environment at home, that becomes our lab. We might even use the resulting services of our lab as production at home. I think of Plex (or any media server), cloud stockage (Nextcloud and al.) — reddit /r/homelab