Concrete Sand has a multitude of uses, ranging from of course concrete, to bedding pipes and, It can also be used as a base material between a vapour barrier and a concrete slab, for installing paving stones, traction sand for roads and sidewalks, and mixing with topsoil and mulch to create a top dressing material for planting lawns.
Concrete Sand and most mortar sands are washed sand products, meaning the dirt in them has been washed away, so anything that you need clean, graded sand for, concrete sand is legitimate option in such cases.