What is this gray circle with a X in the bottom middle of my S7

[cyrusrave]

Just recently I noticed my Samsung S7 has a gray circle with a white X in the bottom middle of the screen, no matter what app I use it is there except for the lock screen.

http://i.imgur.com/salxWBm.png
http://i.imgur.com/9oQuRvH.png
http://i.imgur.com/9YnmweG.png
http://i.imgur.com/PLo1izi.png

 

[Javier P]

Welcome to the forums. What happens if you tap or long press on that icon?