How to back out of an app on iPhone?

So this is my first iPhone and I'm used to Android. On Android, if I click some link or something that opens another app, I can click the back button and go back to where I was, even across apps. Example: I'm using Chrome and click a video link, link opens the YouTube app, when I'm finished, I just click the back button and now I'm back in Chrome exactly where I was when I clicked the link.

Can't find this function on my iPhone yet. I've tried swiping but all I can do is click the home button to back out of the current place and reclick the app where I was.