What does the two boxes over each other on the bottom right on my iPhone mean?

Hello, Ewabeach19.

Thank you for using Apple Support Communities.

To help clarify, is this when you use a specific app? You might be seeing the Continuity feature. Check out this article for more details: Use Continuity to connect your Mac, iPhone, iPad, iPod touch, and Apple Watch Also, using tabs for Safari has the icons you may be referring to: Use tabs in Safari on iPhone

If this isn't the case, let us know with additional details and we'll go from there.

Cheers!