Weight lifting straps come in wide range of quality. Usually, they are made with basic canvas type that is to loop around in wrist and the bar. Some of the weight lifting straps have a Velcro closure that is wrapped around the wrist with a hook which goes around the barbell.
The purpose of this weight lifting strap is to increase gripping strength. They alternate method to increase the grip if someone does not have weight lifting straps then gloves or chalk have a similar affect.