A simple descriptive categorization of the chess opening is King's Pawn Openings, Queen's Pawn Openings, and Others. Since these categories are still individually very large, it is common to divide each of them further. One reasonable way to group the openings is

• Double King Pawn or Open Games (1. e4 e5)
• Single King Pawn or Semi-Open Games (1. e4 other)
• Double Queen Pawn or Closed Games (1. d4 d5)
• Single Queen Pawn or Semi-Closed Games (1. d4 other)
• Flank openings (including 1. c4, 1. Nf3, 1. f4, and others)
• Unusual first moves for White

    The Indian systems (1. d4 Nf6) are the most important of the Semi-Closed Games, and warrant separate treatment.