What is the “Bounce Rate” in Google Analytics?

Bounce Rate is the percentage of single-page sessions on your website. A single-page session occurs when a user lands on a page and then leaves without interacting with that page or navigating to any other pages on your site. This means they didn't click on any links, fill out a form, watch a video, or trigger any other events. The option "The number of times unique users returned to your website in a given time period" describes returning users, not Bounce Rate. "The percentage of sessions in which a user exits from your homepage" is too specific; bounces can occur from any page, not just the homepage. "The percentage of total site exits" refers to exit rate, which is the percentage of page views that were the last in the session, regardless of whether it was a single-page session or not.