Where is this from? Some sort of skin? I don't have a square at all on my Android phone, a Google Pixel (which I assume is "base" Android). You see recent apps by sliding up.
Also the triangle is only an arrow on my phone and the circle is an oval.
It's configurable in Android settings. I think you must have "2 button navigation" option selected? The default is (or used to be) 3 button and looks like the screenshot above, as far as I'm aware
