Shelters are free standing structures that provide shade, shelter and seating.
Shelters are not limited in size, shape or location. The early provision of a shelter was to provide shade but nowadays the norm is to provide a better weathered solution that can be used in inclement weather.
If a shelter is not required on the playground we often use a raised deck. The benefit of using a deck allows structures to be developed which make use of difficult site locations that could be considered unfit to develop (e.g. severe slopes).