What you asking is a little bit confusing.
I use a Screen Mirroring app on my Samsung S7 phone to mirror its screen to my Samsung SmartTV. It can do this because my TV supports MirrorcastDisplay.
I several computers that have graphic cards with multiple output connectors
- AMD FX 8350, GTX 560
- AMD R7 1700X, GTX 1060
How I have hooked up each depends upon what type of output each supports. It may be VGA, DVI-D, or HDMI.
When you add a second display you have the following options:
Primary Screen Only: The second monitor is ignored and only the primary monitor is used.
Duplicate: The second monitor mirrors the primary monitor.
Extend: The desktop of your PC is extended across the two monitors and allows you to have a desktop that spans across both monitors.
Second Screen Only: The primary monitor will be disabled and only the secondary monitor will be used.
Note the second display might be a 2nd monitor, a TV, or a digital projector.
For example for my AMD R7 1700X computer my primary display was a Samsung 23-inch monitor. One time I hooked up the computer to my Samsung TV as a second display using an HDMI cable. For the Windows Display setup I selected Duplicate so what was on my 23-inch monitor was duplicated on the TV.
All that said what exactly are you trying to do?