This opening develops the King to a good spot and allows White to control the center with his king preventing Black from using the weak d3 and f3 squares to attack White's king. White also gains a tempo, which may lead to Zugzwang later, as after Qe1!, forming a King and Queen battery, an Xray attack on Black's King is threatened and Black has to waste a move to respond. Other benefits of the opening include the negation of Back-rank mates as the King is no longer on the back rank and that Black will most likely overextend his pieces in an attempt to launch an assault on the safe White King.
Lack of documentation on the opening forces Black to get out of the book immediately and blunder with moves like Nf6??.
1. e4! e5?? 2. Ke2!!