You use standing wraps after a huge effort to prevent engorgement. They can also be used as transport protection. You put them on the horse above cottons.
For polo wraps: they support the tendon and the fetlock. These have a better support than jumping boots. They are fleece so they keep the member at heat. You can use them in polo or dressage (sometimes in jumping but you have to be careful that it doesn't uncoil).
About sport boots: these are reinforced with elastic, it support the tendon and fetlock but it is very difficult to put them on a horse because if there is a fold, it can lead to tendonitis. This is why usually only professionals use them. It is used after an injury, in dressage and under a cotton.