What are the Real, the Imaginary, and the Symbolic realms?

THE REAL

 The Real is a place (a psychic place, not a physical place) where there is an original unity (an example of this is the unity between the baby and its mother). Because of that, there is no absence or loss or lack; the Real is all fullness and completeness. In the Real there are no needs that can't be satisfied. Since there is no absence or loss or lack in Real, there is no language, language is only needed when what you want is not there.

THE IMAGINARY

In the Imaginary realm, you grasp the idea of others, and begin to understand Otherness as a concept or a structuring principle, and thus begin to formulate a notion of "self". This "self" is in fact an Other, but you misrecognize it as you, and call it "self." (Or, in non-theory language, you look in the mirror and say "hey, that's me." But it's not--it's just an image).

THE SYMBOLIC

The Symbolic realm, which is marked by the concept of desire, is the equivalent of adulthood; or, more specifically for Lacan, the Symbolic realm is the structure of language itself, which we have to enter into in order to become speaking subjects, in order to say "I" and have "I" designate something which appears to be stable.