In Tom's opening speech of The Glass Menagerie, what does he reveal about the nature of the play?
Tom immediately assumes the role of narrator, even though he will also be a main character in the play. "I give you truth in the pleasant disguise of illusion," he says, promising to be not so much a magician as a creator of meaning and truth via the story. So, we immediately understand that we should be looking for some kind of truth made by the fictional story that will soon play out.
He states the setting directly, taking us to the turbulent 1930's and asserts that this will be a "memory play," with everything being fuzzy, dim, emotional, imaginary, and set to gentle background music. The nature of the play, then, is established as more like the inside of a human mind than an actual theater.
Like the incredibly straightforward narrator that he is, Tom gives us the names of the other characters in the play. But then, like the vague and wistful dreamer that he also is, Tom declares that one character (whom we are told in advance about and can identify later as the "gentleman caller") is not so much a real person but a symbol of "the long delayed but always expected something that we live for." This hint prepares us to watch for this character and pay attention to his symbolic role in the story. We understand even more now that the play will be dreamlike and literary, and that it will make a statement about our long-held expectations.
In sum, Tom's opening speech reveals the symbolic, dreamlike, contemplative nature of this "memory play."