A tree stand is a useful hunting tool. It allows hunters to gain an elevated view of the surrounding terrain and avoid leaving a strong ground scent that game might detect. But tree stands can also be very dangerous. They provide a very small surface upon which the hunter kneels, sits or stands. Getting on and off a tree stand safely can be challenging, and then there's the trip up or down the tree to take into account.
Once on the stand, you must stay aware of where you are in relation to the edge of the platform. You shouldn't focus on the target to the detriment of your spatial awareness. And there's also a risk of nodding off to sleep while waiting for game to show up.
That's why you should always use fall restraints and harnesses when you're using a tree stand. In general, a fall restraint tethers a hunter to the tree, not the tree stand. There are many styles of restraints and harnesses. It's important to wear the restraints from when you begin your climb to the moment when you're safely back on the ground again. You should also have a plan on how to safely lower yourself to the ground if your restraint system catches you after a fall.