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The Open Games begin after the moves 1.e4 e5. The name results from the fact that the position often opens quickly which might lead to an early clash of the enemy pieces. Typical examples are the Scotch Opening, the Two Knights Defence or the venerable King’s Gambit. But the most important openings after 1.e4 e5 are the Italian Game and the Ruy Lopez, and here the game often develops more slowly.
The Open Games - A detailed overview - Georgios Souleidis