This opening, a variation of the Giuoco Piano, is named after the British sea captain, W. D. Evans who invented it in the 1820s. With 4.b4 White deflects the Black Bishop from its control of the centre squares and White gives up a pawn to gain rapid development and open lines for his pieces. With 4.b4 White deflects the Black Bishop from its control of the centre squares and This opening is not as popular today as it used to be but it is still played by grandmasters such as Nunn and Timman and Kasparov.
As Steinitz said, "The refutation of a gambit frequently lies in its acceptance." so Black generally accepts the gambit pawn as demonstrated in the following :