While there are instances where and individuals who use
            text and discourse as basically synonymous terms, there is a difference in their
            definitions as regards agents (who and whom) and purpose fulfilled. In text, agents are
            not a critical factor: there may agents, there may not be. For example, in CERN press
            release text, there are none: information is being reported, that's all. In a novel's
            text, there are agents, such as Elizabeth and Darcy in Pride and
            Prejudice, who carry on a conversational discourse amongst themselves that
            the reader observes. The propose of text, therefore, is to relay or communicate
            information and may often be
            non-interactive, meaning the reader of
            the text is an observer.
While
            discourse is used in a nontechnical
            sense to mean conversational communication, linguistics, narratology and literary theory
            have developed a technical meaning to
            discourse. It is this meaning that
            confuses the issue of the difference between text and discourse. To start with,
            conversational discourse as between you and your friend or Elizabeth and Darcy is a
            behavioral event, called a recognizable speech event, that has individual purpose.
            Contrastingly, discourse in linguistics, narratology, and literary theory is a social
            event of multi-layered communication in a variety of media (verbal, textual, visual,
            audial) that has an interactive social
            purpose.
To study text, you study the written words that communicate
            some information: structure, theme, meaning, rhetorical devices, etc. To study
            discourse, you study who is communicating with whom through what medium and for what
            social purpose. Let’s use this answer as an example. To study or analyze the
            text, you will note the overall structure and (most
            importantly!) you will grasp the meaning of the content as it answers your question. To
            study or analyze the discourse, you will determine who is
            communicating with whom through what medium and for what social
            purpose.
Let's analyze discourse together. In this answer I am
            communicating with you through a textual medium--but not you alone. I am also
            communicating with the larger social group made up of anyone who reads this after you
            do--and the discourse goes two ways as you or others comment upon, makes notes about,
            talk about, etc. my side of the discourse. This answer builds an intricate social
            network of participants in a multiple-direction interactive  discourse. What is the
            purpose of this discourse? Well, that is more complex; there may be many levels of
            purpose.
Of the many, the most obvious purpose is to answer your
            question and differentiate between text and discourse. Another purpose is for me to
            articulate ideas about concepts that are important to me. Another purpose is to respect
            your--and other readers--personal background and educational system while I do so. This
            is discourse: it has multiple interactive layers and it has multiple complex social
            purpose.
The same analysis can be applied to your conversation with
            your friend and to the text of Pride and Prejudice: you can find
            the multiple layers in various media that comprise the social event and the various
            purposes of discourse. In summary:
            Text is a behavioral non-interactive event restricted to your experience with
            understanding its characteristics and its meaning or information as its singular
            purpose. Discourse, in any medium, is a social interactive event with many layers of
            communication and many layers of purpose.