My dad was visiting with me the other day and I was showing him some of the basics on his new iPhone.
When I explained how to close out his apps and tabs, (imagine a deer in headlights), we discovered that he had hundreds of tabs open on his phone.
Closing one at a time would have taken all night but with a couple of quick taps, all his open windows/tabs were closed in just a few seconds.
Hope you find this helpful!