Scandinavian Defense is a chess opening with the ECO code B01. It goes 1. e4 d5. White opens with 1. e4 (the king's pawn) and Black answers 1... d5. After 2 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 2. exd5.
Black hits e4 immediately with 1...d5. After 2.exd5 Black takes back with the queen or the knight.
chessGM has a full course for this line: open the Scandinavian Defense course lesson.