The bounce rate measures the number of visitors to a website that leave before a specified amount of time has elapsed (this time period varies among analytics tools, but typically it is 30 minutes). This means that if a user accesses your site and leaves it within 30 minutes or leaves their browser idle for that time, they will be registered as a bounce. The bounce rate for an individual page of a website is determined by the number of users that access a page and leave the site without clicking to another page within the specified time period.
When you're looking at specific pages on your site, especially in terms of the search keywords that bring visitors to those pages, bounce rate indicates the number of people who come to one landing page on your website and then leave without viewing any additional pages.
You should constantly strive to lower your bounce rate. The lower your bounce rate, the more people are digging deeper into your site's content – and the more content they interact with, the more likely they are to convert or engage your company.
As an example, Newfangled used to have a popular blog post on "National Donut Day." It had a high number of visits but an extremely high bounce rate (and it has since been removed because of this). Anyone searching for National Donut Day (#1: customer intent) did find what they were looking for on this page (#2: landing page purpose), but Newfangled's overall website purpose (#3) has nothing to do with celebrating this tasty holiday – so these users bounced from our site.
On the other hand, if someone searched for "website development" (#1) and landed on our Development page (#2), they would be far more likely to stick around and check out other site content, since their intent and our overall site purpose (#3) are a direct match. When all three elements align, a user is less likely to bounce.