Reed is a common name for tall, grass-like plants of wet places. They occur in reed beds. They are all members of the order Poales.
Reeds are many polyphyletic species, which have all adapted to this wet habitat by convergent evolution. It is a "form" name, not a technical botanical term.
Phragmites australis, the common reed, is used in many areas for thatching rooves (roofs). When thatched rooves were common, rivers were harvested for reeds every year. The reeds were stored in barns, and purchased by roofers for thatching. In the United Kingdom, common reed used for this purpose is known as "Norfolk reed" or "water reed". However, "wheat reed" and "Devon reed" are not reeds but long-stemmed wheat straw.
In Britain, thatching began to be less used in the early 19th century. It was replaced by slates from quarries in Wales. Later still, slate tiles were replaced by the cheaper mass-manufactured plastic tiles.