What keys to press to cut the background like he did in this video

[Chris23483841eh56]

Hello! Could you please answer what hotkeys did he pressed in this video after selecting mask from channels and then inverting it to cut the background?

video time stamp: 26:51 https://youtu.be/o5SwLGgKy6U

[Chris23483841eh56]

I pressed ctrl + x and my mask is gone

[Bojan Živković]

Be careful what is activated/ selected in the Layers panel. Select/click on layer with pixel information that you want to delete, do not select layer mask. 

As already mentioned by @Jeff Arola author is using Delete or Backspace key to delete content and probably Alt + [ to move through layer stack in the Layers panel.

And by the way, selection must be active while pressing keyboard shortcut.

[Jeff Arola]

Most likely the Delete key on the keyboard.

That corresponds with Edit>Clear in photoshop.

[Chris 486]

I would also assume the delete key.