I would guess they're usually referring to over-the-board (OTB) ratings, but I'm not sure. You could try a few and see what seems over your head and get a general gauge from there.
which rating ?
When titled players talk in videos, they should be referencing ~FIDE or ~USCF which are close anyway. They would never be talking about an online rating unless specifically stated.
When people talk on the forums, they usually mean chess.com rating (whichever one they're most active in). Unless they're an experienced player, then just like the videos they'd never mean an online rating.
Sometimes you have to interpret it from the context. In tournament and professional play, no one cares or talks about online ratings.
If you need help, please contact our Help and Support team.
I play online and live chess and have different ratings for each. So when people talk in general terms about ratings (for example learning videos and mentoring are recommended for certain ratings) which rating are they referring to ?