Chosen Solution
Anyone has any idea what is this?
If its permanently like that, my only guess is a damaged lcd. I might be wrong though. I wouldn’t take it to Apple because they are going to tell you to get a new computer especially because yours is from 2015. Go to a 3rd party place or computer store to get a full diagnosis.
@anamiami - Lets do a few tests here to isolate the issue. What does an external display show? If it is still messed up then the logic board needs attention. If the image on the external is OK we then know the issue is within the internal displays data pathway or the display its self. Did you drop or bang your system or sit something heavy on the lid? Did you have a liquid spill at some point or sit the system down on a wet surface? A bang would have damaged the circuitry within the lid. A liquid spill could have damaged the display connector and its cable. The driver logic on the logic board could also be damaged.
