Thin straps are used as part of clothing or baggage, or bedding such as a sleeping bag. See for example spaghetti strap, shoulder strap. A strap differs from a belt mainly in that a strap is usually integral to the item of clothing; either can be used in combination with buckles.
Straps are also used as fasteners to attach and bind items, to objects, animals (for example a saddle on a horse) and people, or even to tie down people and animals, as on an apparatus for corporal punishment. Occasionally a strap is specified after what it binds or holds, e.g. chin strap.