You probably clicked on the little piece here thinking, "What does this do?"
you see how big the GPU is? It takes up the whole width and length of the computer, and it's only connected by a small strip connected to a single slot on the motherboard. All the weight is going to sag and damage the card, right? That's where this support beam comes in- You adjust it, then place it under so it stays at an even level.
these things are fairly cheap and have good integrity. Though like with RGB, some people use legos or action figures to help keep their GPU up.
Maybe I should ask Superman to support my GPU...