Smoke and mirrors
Smoke and mirrors is a idiom for a deceptive, fraudulent or insubstantial explanation or description. The source of the name is based on magicians' illusions, where magicians make objects appear or disappear by extending or retracting mirrors amid a distracting burst of smoke. The expression may have a connotation of virtuosity or cleverness in carrying out such a deception.
In mathematics, 'Name is Smoke and Mirrors' ('Name ist Schall und Rauch', literally: 'name is sound and smoke' in German) from Goethe's poem Faust was Henri Poincare's response to Felix Klein's vexation of Poincare's creation of the term 'the Kleinian function for all other cases of S'.
In the field of computer programming, it is used to describe a program or functionality that does not yet exist, but appears as though it does. This is often done to demonstrate what a resulting project will function/look like after the code is complete — at a trade show, for example.