Bounce rate is the share of visits to a page that ended there, with the visitor leaving without clicking to a second page or doing anything the site could measure. A high number can mean the page failed, but it can also mean the page answered the question or showed a phone number that was then dialled.
GA4, the current Google Analytics, no longer leads with bounce rate. It shows engagement rate instead: the share of visits that lasted more than ten seconds, viewed a second page or triggered a conversion. Bounce rate in GA4 is simply everything else, so the two always add up to the whole.
