A series of rows is a term used to describe a structure that consists of multiple rows of items placed one after the other. It can be used to refer to a variety of things, such as a set of books on a shelf, a line of people waiting in line, or a row of houses. The term 'TIER' is a four-letter word that is often used to describe this type of structure, as it implies that the items are arranged in levels or tiers.