The opening scene of a play that provides background information and introduces the central conflict

It is "Prologue" in traditional plays which the opening scene of a play and provides background information and introduces the central conflict.

Explanation:

Prologue in Ancient Greek and Roman plays as well as in Elizabethan plays used to serve slightly varying purposes.  However one of the most common purposes served by prologue (which is the opening scene of a play) is to provide necessary background information and to introduce the central conflict of the play.

Prologue in Sophocles' tragedy "Antigone" provides the background information about the war between two of Antigone's brothers and their killing each other. The conflict of Antigone's violating the law by King (Creon) is also provided here.