The three metrics are are all different.
Bounces: the number people that come to your website, view one page, and leave.
Exits: The number of people who exit from the site on that page. This metric counts sessions that start anywhere on the site.
Drop offs: A drop off occurs when someone exits the user flow that you are viewing. This does not necessarily mean that they are leaving the website.
For example if you set up a behavioral flow to track people who move from page
A -> B -> C, and someone goes from page
A -> F this will count as a drop off because it does not follow the flow that you have highlighted.
Thus, the behavioral flow in the photo is not implemented correctly. I would recommend reading up on flow reports here, and here.