The double king's pawn opening in chess refers to the sequence where White plays 1. e4 and Black responds with 1... e5. This is one of the oldest and most fundamental openings in chess, leading to many classic variations like the Ruy Lopez, Italian Game, and Scotch Game. The other options (e3-e6, d4-d5, d3-d6) represent different pawn structures or incorrect move orders.