Macbook Pro screen display problems

I am using a Macbook Pro (the 2015 model A 1398).

Just overnight my screen shows strange horizontal lines as this:

These horizontal lines are roughly gathered in the same place on the screen (on the top), and they may increase or decrease the numbers, from time to time.

However, if I do the print screenshot, I do not see any such horizontal lines.

I did not hit or hurt my Macbook Pro recently. Can someone give any advice on how to fix it? I had restarted, shut down and restart a few times, but the problem still persists.

Info:

Thanks experts for the help!

Since you have a 2015 MacBook Pro that uses Integrated Graphics (the Intel Iris Pro chipset), you can be assured that what is manifested on one screen, will manifest on all.

What this means is that the lines you are seeing on the screen are not due to failing GPU but rather the LCD itself. You confirmed this by plugging your MBP into an alternate display device (projector).

If you have this under Apple Care, you should take it in to have it repaired straight away. To fix this, you will need to replace the entire Display Assembly and unfortunately, they are very expensive (approx. $850USD).