Vienna Game: Max Lange Defense is a chess opening with the ECO code C25, part of the Vienna Game family. It goes 1. e4 e5 2. Nc3 Nc6. White opens with 1. e4 (the king's pawn) and Black answers 1... e5. After 4 moves it is White to move. The lesson on the board explains every move of the line and lets you play it yourself; it is free.
In chessGM's opening book this position continues with 3. Bc4.
After 1.e4 e5, White plays 2.Nc3 instead of Nf3. It keeps the f-pawn free, so White can later play f4 like a King's Gambit.
chessGM has a full course for this line: open the Vienna Game: Max Lange Defense course lesson.