Comfort Zone - Something where you are comfortable being. I do not feel awkward, I do not feel anxious. This is my comfort zone.

Safety Circle - Something where you may not be comfortable but you feel safe to experiment without being judged or without the fear of failure.

A leader’s responsibility is NOT to create comfort zone. Comfort zone is not necessarily good for that their team or the organisation. A leader SHOULD CREATE a safety circle and push their team to operate outside the comfort zone. This is what I would call it as raising the bar.

PS - Comfort Zone is always perceived as being in the safety circle