Your photo suggests that you have a screen protector fitted to your iPad.
If so, it would appear that the screen protector adhesive is separating from the screen - potentially due to dust or trapped air bubbles between the iPad screen and the inner (adhesive) surface of the screen protector. If you are unable to smooth-out the screen protector adhesive by applying gentle and even pressure with a squeegee (or similar), the only remedy is to remove an refit the screen protector...
Assuming that the screen protector is laminated glass, using a fingernail, very gently lift the corner of the screen protector - allowing the adhesive to slowly relax as you lift from the corner.