What is the line on my laptop?

What is that black line? It is getting bigger. Does it still go away? If so can I get it repaired?

And please just formulate your answers, I don't know anything about that, because it's my father's old laptop.

Your laptop is broken so the screen was like that for me

Can the line be seen in every program?

Actually, it looks like it is normal text that is displayed far too small. But maybe the screen is over.