Laptop black screen

[NUJABE]

Hello I need help okay so I have a HP laptop it's on Windows 10 and everytime I boot it up it seems to be fine but on the login it's a black screen but when I plug it up to the external monitor everything is perfect but the thing is when I click on an app or example control alt delete it shows up on my laptop screen is it a dead screen or do I have a lot of stuff on my desktop? Please help

 

[hang-the-9]

Does the BIOS screen show normally on the laptop screen? When exactly does it go black? Is it fully black with no light or can you see a backlight? Any more details about the issue like what happened before the issue started?