I used my coworker's iPhone yesterday, opening a link from a text message, and couldn't figure out how to go back to the message. Swiping in from the left side went back... within the browser, which had no back history. I had to go to the home screen and open text messages again.
On Android, you just hit the back button and it goes back to the previous app in the stack if you launched one app from another.
If you want to go back to the previous app you can swipe from the left on the home indicator, or on older iPhones swipe from the left with force.