Who is Will Eisner from Understanding Comics and what is their importance?

Described as a master comics artist, Will Eisner is referred to several times in the book. Eisner is the one credited with coining the term, "sequential art," as an accurate way to describe comics as a medium. This definition will prove critical in McCloud's analysis, since a singular image in the newspaper, even in the Comics section, for example, does not fit into the definition. McCloud points out that a sequence of one is no sequence at all.