What is the thing in bird box?

In the movie "Bird Box," the thing is a malevolent force or entity that takes the form of each person's worst fear or sorrow, driving them to madness and ultimately causing them to commit suicide. It is never fully explained or shown on screen, with the characters only able to perceive it through distorted whispers and sounds. The thing is believed to have originated in Eastern Europe before spreading across the world, leading to a post-apocalyptic scenario where survivors must blindfold themselves to avoid looking at it and succumbing to its influence. The thing is a central element of the movie's plot and serves as a terrifying and mysterious antagonist.