What bounce rate is: the rate at which your visitors “bounce” off of your site (meaning leave your site) without visiting any other pages within your site; calculated by taking the total number of visitors who view one page only, and dividing that by the total number of visitors on the site who entered from that page.
What bounce rate not: exit rate.
Why we care about bounce rate: Your bounce rate can tell you how effective your entry page (or landing page) is. If your entry page has a high bounce rate, your visitors are mostly either clicking to other sites or closing their browser windows while they’re still on the entry page.
This post is part of an ongoing Clickipedia series, defining all the terms you need to know for conversion rate optimization. Keep checking back each week to learn more, and don’t forget to check out the whole series.