The computer will also tell you that it’s establishing a connection. And soon enough (if it works at all: no promises, remember!) what’s appearing on your phone will also appear on the computer screen:
Pick a photo from your phone’s gallery and up it will pop on the computer display:
It doesn’t have to be an Android phone sending the screen. Here is the screen of my Microsoft Surface Pro 4 mirrored to a Windows Desktop computer. But I guess that might be a solution to a problem which doesn’t exist….