The concept was introduced into psychoanalysis and literary theory by Jacque Lacan.
Lacan introduces a three tier concept of its development as: an individual's progress from state of plenitude, to scarcity which is succeeded to the state of desire vs. lack.
It's interesting that Lacan merged linguistics as well as psychoanalysis to produce his theories.
For Lacan, the state of 'plenitude' exists in an individual only up to the point where the ego is formed. 'Plenitude' is the state of being nourished and also marks the stage where the individual is not weaned.
The formation of the ego is called the 'mirror stage,' where the individual learns to live with the concept called [I], and learns to differentiate the 'other' as objects. Lacan's metaphoric use: 'mirror stage' develops the process that the individual becomes a reflector as well as a reflective surface of images, and he mentions that this stage is important in the development of the individual's psychosocial identity, or, the identity of the individual as language's [I] with objects called the [others].
However the child's entry into the 'mirror' stage is never easy coz the identity that is formed through identification with images enforces mastery of the subject. What remains before the 'mirror stage' as the individual, also called the 'Real' becomes alienated.
Scarcity as symbolic state of (self identity), formed as the Ego is never total or complete and it creates the conflict with Real.
The 'REAL' is a complex and confusing term used by Jacque Lacan. Lacan was himself critical of it during his initial development and even called it as "spat out chewing gum". Wonder why? "Laugh at your real if you can!"At other times he has called it a "void." However, the real as a concept was more empathically and intelligently developed by Philosophers who revised Lacan especially Julia Kristeva (psychoanalyst who trained under him). She, rather than negating the REAL as derogatory blemish, gave realization to its existence as "subjectivity."
The "REAL" can be explained with a few examples. The sounds of ecstasy and agony are 'realizations' of the real.The symbols produced as "dreams" coming from the "unconscious" are other examples of the "real." Beyond the boundaries of the symbolic scarcity called "ego," the real emerges. In one sense the real becomes the 'other' of one's ego. I would like to revise both Lacan and Kristeva by mentioning that not only does the "real" speak (non cognitive language[language of ecstasy and agony]), it also sees (dreams as symbols), it also feels [the affected] as body states. The real can transgress the [codes] of the both the ego's world and the super ego. What ever is expressed by the real transcends both the ego and the laws sustaining it as the super ego.
Lacan was extremely obsessed with the idea of connoting the "phallus" as a non sexual object, universal to gender as a language tool to express the symbolic world or the world of the real. And, he amusingly connotes it symbolically as a non-sexual tool(sexualized with gender and construct) to symbolize the expression of the ego as the language of the [I] taking the symbolic to express itself with the other [objects]. Lacan's phallusiszezation (neologism) has been criticized by deconstructive philosopher -Jacque Derrida as being phonetic and centric- centering the imagination called the psychoanalysis of a sign as the formed ego. Post structural feminists (some of them) take a multi-labial-polysemous view of the ego's symbolization. They create a (hermineutrics) (neologism used to compensate hermeneutics) of discourse to examine the problem why the [ego] has to be constructed as the symbol of a male organ. Julia Kristeva has done much work on the 'semiotics' of language as it exists before the symbolic state (another essay on it will be written).
From the phallus as the signifier of the language of the Ego with its scarcity, Lacan moves to top most hierarchy of the symbolic realm-desire vs. lack. Here, for Lacan, the phallic signifier becomes a super 'signifier', taking the 'signified' of society's symbolic codes as 'laws of the earthly (Lacan uses the term earthly father[not me])' that is, the ego is absorbed into the symbolic structure of warnings that there are laws and norms and violation would lead to punishment as consequences. Examples of such laws are civil, criminal, political, & personal laws. As a psychoanalytic discourse, the "laws" or the "super phallus" has limited liberty. It's normative and based on the level of freedom that a society can sanction as convention. The inverse irony of it is: it emphasizes the freedoms and liberty through its enforcement. It is rather problematic that individual's ego is tethered to a super-phallus producing within the individual the state of desire and its inverse lack. The "super phallus, "or the laws of the earthly father, or the super-signifer, or a Hammurabi-democratized or an eye for an eye and tooth for a tooth, sanitized to promote ethical conscience as well individual liberty becomes conflictual when its restricts the ego and alienates the real.