To all pageviews to the page, the exit rate is the percentage that did the last in the session. Means, exit rate is the percentage of users that left your site from a page.
A page view on your business websites is not just a page view for Google Analytics. Google Analytics on the context of what the visitor did before page view and what he did after for assign the view for one of a number of actionable metrics.
The Google Analytics exit rate is a page metric that looks at how often visitors leave your website after viewing a particular page. Easy put, an exit rate for a page measures the number of visitor sessions on your site which included various page views and ended with that particular page.
This is important for the note that this number does not represent the percent of your website so the total viewers who leave your website after viewing a particular page, but rather the percentage of visitors who viewed that page during the course of their visit and left your website immediately after seeing the page.