ECO stands for Encyclopedia of Chess Openings and is the standard way of listing all the openings. It is the standard. I also believe they release new more Extensive ECOs but the main stuff listed below never changes.

<>A is stuff like English Opening, Reti, Benoni,Dutch Defence. . .

               A  A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 

<>B is stuff like Sicilian Defense, Caro-Kann, Pirc, Modern, Alekhine, Scandinavian
               B  B0 B1 B2 B3 B4 B5 B6 B7 B8 B9

<>C is stuff like Ruy Lopez, The French, King’s Gambit

               C  C0-C1 C2 C3 C4 C5 C6 C7 C8 C9 

<>D is stuff like Queen’s Gambit, The Slav, Gruenfeld, Queen's Pawn Game...  

               D  D0 D1 D2 D3 D4 D5 D6 D7 D8 D9 

<>E is stuff like King’s Indian, Nimzo-Indian, Queen’s Indian

               E  E0 E1 E2 E3 E4 E5 E6 E7 E8 E9 

Log in or registerto write something here or to contact authors.