The Glass Menagerie is a memory play, which is a term that was first coined by Williams in reference to this work. A memory play is narrated by its lead character (in this case, Tom) from his memory. Tom recalls the period of his life before he leaves his family in St. Louis to pursue his own dreams. In the following passage from Scene 1, Tom describes to the audience some elements of a memory play:
The play is memory. Being a memory play, it is dimly lighted, it is sentimental, it is not realistic. In memory everything seems to happen to music.
The play is described as "not realistic," implying that certain features of the play may extend beyond what is considered conventionally appropriate in theater. Williams himself explains in the play's introduction that there is an "unusual freedom of convention" in depicting memory, as certain aspects of memories are exaggerated or forgotten due to human subjectivity. Thus, Williams grants himself a freedom to construct his story without a commitment to making it realistic. Rather, he is able to tease out truths and messages according to his desire. With The Glass Menagerie, Williams ultimately created a new genre of theater that other playwrights adapted in the future.